Use of marine algae for co-producing alkenones, alkenone derivatives, and co-products

ABSTRACT

A method comprising a series of selective extraction techniques for the parallel production of biodiesel and isolation of several valuable co-products including an alkenone hydrocarbon mixture of the kerosene/jet fuel range (primarily C10-, C12-, and C17-hydrocarbons) and fucoxanthin, a high-valued carotenoid, from the marine alkenone-producing microalgae  Isochrysis.

PRIORITY

This application is a continuation-in-part of U.S. application Ser. No.14/187,929, filed Feb. 24, 2014, now pending, which is acontinuation-in-part of U.S. application Ser. No. 13/298,576, filed Nov.17, 2011, now pending, which claims the benefit of priority of U.S.Provisional Patent Application No. 61/414,491 filed Nov. 17, 2010, andwhich is a continuation-in-part of U.S. application Ser. No. 12/967,478,filed Dec. 14, 2010, now abandoned, which claims the benefit of priorityof U.S. Provisional Application No. 61/287,585 filed on Dec. 17, 2009,and this application is also a continuation-in-part of U.S. applicationSer. No. 13/298,576, filed Nov. 17, 2011, now pending, which claims thebenefit of priority of U.S. Provisional Patent Application No.61/414,491, filed Nov. 17, 2010. The entire contents of each of theabove referenced applications are incorporated herein by reference andwithout disclaimer.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was supported in part by the United States Governmentunder National Science Foundation Grant No. CHE-1151492, and in part bythe State of Massachusetts under Massachusetts Clean Energy Center GrantNo. 16489900. The Government has certain rights in this invention.

FIELD OF THE INVENTION

The present invention describes improved methods and extractiontechniques for the parallel production of biodiesel, alkenones, alkenonederivatives including an alkenone hydrocarbon mixture of thekerosene/jet fuel range (primarily C10-, C12-, and C17-hydrocarbons),and isolation of valuable co-products including fucoxanthin, ahigh-valued carotenoid, from marine algae.

BACKGROUND OF THE INVENTION

Increased global demand and consumption of easily accessible petroleumand natural fossil fuels continues to be unpredictable in future pricesand put a constant pressure on economies, politics, and importantly, theenvironment. These pressing issues have led to a growing need foralternative, renewable, and sustainable energy sources and additionaldevelopments in production of alternative fuels.

Currently, the largest volume of renewable fuel sources or biofuels isderived from agricultural feedstocks including plant-based sugars andoils (i.e. carbohydrates and acylglycerols, respectively) and otherderivatives. However, reliance on edible crop-based fuels is not along-term energy solution since premium farmland, abundance of water,and energy are in limited supply. Therefore, it is beneficial to seekout additional sources for biofuels and efficient methods of production.

In recent years, potential biofuel sources such as algae have shown tobe promising alternatives to crop-based biofuels. Advances incultivation, processing, and production have demonstrated not only thefeasibility of using algal sources in terms of cost, labor, and time,but also the potential value in parallel production of commerciallyuseful co-products.

Algae can produce 10 to 100 times as much mass as terrestrial plants ina year. Algae also produce oils (lipids) and starches that may beconverted into biofuels. Algae useful for biofuel production includealgae known as microalgae, consisting of small, often unicellular,types. These algae can grow almost anywhere, though most are commonlyfound at latitudes between 40 N and 40 S. With more than 100,000 knownspecies of diatoms (a type of algae), 40,000 known species of greenplant-like algae, and smaller numbers of other algae species, algae willgrow rapidly in nearly any environment, with almost any kind of water,including marginal areas with limited or poor quality water.

While the cost of petroleum has increased dramatically in recent years,critics remain who contend that nonetheless algal biofuels will provetoo costly to manufacture on a larger scale, and that algaeproductivities do not surpass those of irrigated crops and cultivating,harvesting, and processing microalgae is simply too expensive. Addingthe production of both supplementary biofuels and valuable co-productscan make energy production using algae commercially viable and a keyreason to further explore algae as a biofuel source.

The most notable product yielded from algal biofuel production isbiodiesel in the form of long-chain alkyl esters and more specifically,fatty acid methyl esters (FAMEs). However, another unique and promisingclass of algal compounds known as long-chain alkenones (e.g. alkenones)are naturally biosynthesized by certain species of algae, namely membersof the Isochrysis, Emiliania, and the Gephyrocapsa families, in parallelto compounds required for biodiesel production. Alkenones may beconverted to smaller hydrocarbon fragments in the range of jet fuel andkerosene through a separate processing method than utilized forbiodiesel/FAME synthesis. Thus, jet fuel-range biofuels may be producedin parallel with biodiesel from a single batch of algae, adding anotherlevel of commercial value.

Additionally, from this single batch of algae, it is possible tosimultaneously isolate other valuable co-products such as fucoxanthin,astaxanthin, beta-carotene, and other carotenoids. Fucoxanthin, inparticular, has been reported for health benefits as an antioxidant,anti-inflammatory, anti-cancer chemical with industrial uses as well.Therefore, there is an unmet need and desire to use algae not only as adiversified source of biodiesel which does not rely on food resources,but as an economically viable source of biodiesel, biofuel, andadditional desirable co-products.

SUMMARY OF THE INVENTION

In accordance with the present invention, parallel methods are providedfor producing alkenone derivatives and commercially valuable co-productsfrom algae. In one aspect, the disclosure provides a method whichcomprises: (a) culturing an alkenone-producing alga under a growthcondition sufficient to produce alkenones within the alga; (b)separating the biofuel oil comprising the alkenones from the biomasscomprising the valuable co-products; (c) isolating the alkenones fromthe biofuel oil; (d) chemically modifying the alkenones to producealkenone derivatives of a hydrocarbon length in the range of liquidtransportation fuels (e.g. jet fuel, kerosene); and (e) chemicallymodifying the biomass to produce co-products.

In certain embodiments, the alkenone-producing alga is a species of theIsochrysis family, such as Isochrysis galbana, Isochrysis sp. T-iso, andIsochrysis sp. C-iso. The alkenones of the alga may comprise alkenoneshaving a number of carbons ranging from 30 to 42. The alkenones may beconverted to alkenone derivatives by a cross metathesis reaction. Incertain embodiments, the alkenones are processed into a liquid fuel suchas diesel and gasoline. In other embodiments, the alkenones areprocessed into a gaseous fuel, such as a syngas (a mixture of CO and H2)and/or a synthetic hydrocarbon gas (e.g. methane, propane, and butane).In certain embodiments, the alga also produces fatty acids andby-products (e.g. acylglycerols). Optionally, the method comprisesconverting a mixture of fatty acid compounds and alkenones to products(e.g. alkenone derivatives, FAMEs, etc.) without separating the fattyacid compounds from the alkenones. In certain embodiments, the growthcondition for culturing the alga may include a stationary growth phase,a high temperature, sufficient light, nutrient limitation or acombination thereof. In certain specific embodiments, algae are directlyconverted into methane via hydrothermal gasification.

Additionally, the waste-stream (i.e. the biomass) normally discarded inthe production of biodiesel and alkenone derivatives may be processed toproduce co-products with a monetary value without alteration of thealgae-to-biodiesel/algae-to-alkenone derivatives processes. In oneembodiment, the isolated biomass is extracted to produce valuablecarotenoids such as fucoxanthin.

Optionally, growing of algae and hydrothermal processing of algaebiomass are coupled into a continuous process. In certain embodiments,chemically modifying the alkenones comprises pyrolyzing or cracking thealkenones. In some embodiments, alkenone derivatives of step (b) areacrylic acids, acrylic esters, alkenes, vinyl chloride, vinyl acetate,diacids, diamines, diols, or lactic acid.

In certain aspects, the disclosure provides modified algal strains whichmay enhance the products derived from the claimed methods.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1. Schematic of the co-production processes of alkenones 9,alkenone derivatives 12, and co-products 16.

FIG. 2. Structures of a common alkenone 9 produced by Isochrysis sp. (a)and common FAME methyl linoleate 6 (b). Nomenclature for both is # ofcarbons: # of double bonds, however, note that the configuration ofdouble bonds is different.

FIG. 3. Picture of pure alkenones 9 showing that these compounds arewhite, crystalline solids at room temperatures isolated in multi-gramquantities from Isochrysis (typically 4 g from 25 g of the biofuel oil4).

FIG. 4. GC-FID chromatograms for starting alkenones 9 (a) andbutenolysis products 12 (b) obtained by reaction 11 with cis-butene andcatalyst Ru-HG for 1 h (Entry 6, FIG. 15) showing complete consumptionof the alkenones 9. For those reactions giving incomplete conversion,undissolved alkenones 9 could be observed in the reaction mixture(inset).

FIG. 5. Results from butenolysis kinetic experiments by analyzingaliquots from a single reaction with percent conversions normalized tothe GC-FID peak area of methyl stearate as an inert internal standard.The apparent decrease during the first 10 minutes is due to initialalkenone solvation.

FIG. 6. GC×GC-FID chromatogram of the alkenone butenolysis productmixture 12 obtained after 30 min using cis-2-butene and catalyst Ru-HG.Molecular ion identifications were made by analyzing equivalent peaks inthe GC×GC-TOF chromatogram. Note the exceptional resolution allowing foridentification and quantification of E,Z-isomers.

FIG. 7. GC×GC-TOF chromatogram “plan view” of the alkenone butenolysisproducts mixture 12 showing separation of compounds into differentsubclasses.

FIG. 8. UV absorbance spectra of red fractions 16 obtained bychromatography 15 of the neutral lipids (left) and a fucoxanthinstandard solution (right) showing characteristic maxima at 446 and 475.

FIG. 9. HPLC chromatogram of the biomass oil 3 (A) and fucoxanthinstandard (B, inset).

FIG. 10. ¹H NMR spectrum (500 MHz CDCl3) of the extracted biomass oil 3(top), the fucoxanthin fraction 16 obtained from the biomass oil 3(middle), and the fucoxanthin standard (bottom).

FIG. 11. Cross metathesis (CM) and the reverse ethenolysis 11.

FIG. 12. Mechanism of ethenolysis (X═H) and butenolysis (X═CH3) 11.

FIG. 13. Comparison of methyl oleate and alkenone butenolysis reactions11.

FIG. 14. Comparison of fatty acid, alkenone, and botryococcenestructures for consideration as a biofuel feedstock.

FIG. 15. Results from butenolysis reactions 11 of alkenone mixtures 9isolated from Isochrysis.

FIG. 16. Alkenone composition 9 and expected butenolysis products 12.

FIG. 17. Yields and fucoxanthin content 16 for the biofuel oil 4 and thebiomass oil 3 obtained by sequential hexanes/ethanol extraction 2 of dryIsochrysis algae culture 1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides parallel methods for co-producingalkenones and alkenone-derivatives suitable for use as biofuel, inparticular jet fuel and/or kerosene and valuable co-products from asingle batch of algae.

Unless otherwise defined herein, scientific and technical terms used inthis application shall have the meanings that are commonly understood bythose of ordinary skill in the art. Generally, nomenclature used inconnection with, and techniques of, chemistry, molecular biology, celland cancer biology, immunology, microbiology, pharmacology, and proteinand nucleic acid chemistry, described herein, are those well-known andcommonly used in the art.

Throughout this specification, the word “comprise” or variations such as“comprises” or “comprising” will be understood to imply the inclusion ofa stated integer or groups of integers but not the exclusion of anyother integer or group of integers.

The singular forms “a,” “an,” and “the” include the plurals unless thecontext clearly dictates otherwise.

The term “including” is used to mean “including but not limited to.”“Including” and “including but not limited to” are used interchangeably.

The term “substantially pure” as used herein refers to a chemical thatis chemically pure or analytically pure—this the chemical has a puritygreater than 70%, greater than 75%, greater than 80%, greater than 85%,greater than 90%, greater than 95%, greater than 8%, or greater than99%.

The term “co-product” means a product that is prepared in the presenceof another product.

The term “commercially useful product” is used to define a product whichhas monetary value and/or economic demand, wherein an economic demand isdefined as an economic principle that describes a consumer's desire andwillingness to pay a price for a specific good or service.

The term “polar solvent” refers to a solvent wherein there is either apermanent separation of positive and negative charges, or the centers ofpositive and negative charges do not coincide, in the molecules. Polarsolvents include, but are not limited to chloromethane, dichloromethane,dichloroethane, tetrahydrofuran, dimethylformamide, acetonitrile,nitromethane, propylene carbonate, formic acid, butanol, isopropanol,methyltetrahydrofuran, trifluoromethylbenzene, ethyl acetate, ethylether, acetone, dimethyl sulfoxide, alcohols, acetic acid, and esters.In some embodiments, the polar solvent is selected from the group ofdichloromethane, dichloroethane, tetrahydrofuran, methyltetrahydrofuran,ethanol, and other alcohols.

The term “non-polar solvent” refers either to a solvent withoutsignificant partial charges on any atoms (e.g. hydrocarbons) or to asolvent in which the polar bonds are arranged in such a way that theeffects of their partial charges are cancelled out (e.g. chloroform).Non-polar solvents include, but are not limited to, hydrocarbonscontaining 1 to 22 carbons, benzene, toluene, xylene, pentane,cyclohexane, n-heptane, n-hexanes, octane, iso-octane, chloroform,ether, dimethyl ether, diethyl ether, methyl-tert-butyl ether,1,4-dioxane, and neutral or non-ionic surfactants. In some embodiments,the non-polar solvent is selected from n-hexanes, iso-hexane, n-heptane,and iso-heptane.

The term “more polar than hexane” refers to a solvent with a greaterseparation in electromagnetic charges between atoms than hexanes whereinhexane consists of equal sharing of electromagnetic charge betweenatoms. Solvents more polar than hexane include but are not limited toethanol, methanol, chloromethane, dichloromethane, dichloroethane,tetrahydrofuran, methyltetrahydrofuran, ethyl acetate, acetone, dimethylsulfoxide, alcohols, acetic acid, esters, ketones, amines, carboxylates,and halogenated hydrocarbons.

The term “biofuel oil” refers to the extracted oil obtained from theextraction with solvent #1 comprising a fatty acid-rich fraction (e.g.fatty acids, fatty acid derivatives) and a lipid-rich fraction (e.g.lipids, alkenones).

The term “biomass oil” refers to the extracted oil obtained from theextraction of the algal biomass with solvent #3 of which comprisesco-products.

The term “biomass” or “algal biomass” refers to the algal cellulardebris (e.g. cellular residue, enzymes, by-products, etc.) removed ofthe biofuel oil obtained by extraction with solvent #1.

The term “alkenone derivatives” refers to the products derived fromalkenones or chemical modification of alkenones.

The term “minimal amount of light” refers to the minimal amount of timewhich the reaction, reagents, products, etc. (e.g., the reactionmixture) are in the presence of light. In some embodiments, the term“minimal amount of light” is exposure of 0 seconds, exposure of lessthan 5 seconds, exposure of less than 10 seconds, exposure of less than15 seconds, exposure of less than 30 seconds, exposure of less than 1minute, exposure of less than 2 minutes, exposure of less than 3minutes, exposure of less than 4 minutes, exposure of less than 5minutes, exposure of less than 6 minutes, exposure of less than 7minutes, exposure of less than 8 minutes, exposure of less than 9minutes, or exposure of less than 10 minutes.

The term “alkenone-enriched sample” refers to a sample comprisingalkenones and lipids.

The term “non-alkenone containing sample” refers to a sample obtainedfrom the aqueous phase of the 2-phase mixture of the polar extraction ofthe algal culture which may be the waste-stream discarded in theproduction of biodiesel.

The term “alkenone-enriched phase” refers to the first polar phase (e.g.polar phase) of the two-phase system of the algae extraction whichcomprises lipids and alkenones.

The term “commercially valuable second molecule” or “commerciallyvaluable second product” refers to at least one product obtained fromsecond phase of the two-phase system of the algae extraction.

Algae Species as a Feedstock and Alkenone Source

Algae can store energy in the form of either oil or starch. Stored oilcan be as much as 60% of the weight of the algae. Certain species whichare highly prolific in oil or starch production have been identified,and growing conditions have been tested. Processes for extracting andconverting these materials to fuels have also been developed. Asreferred herein, the terms “lipids” and “oil” are used interchangeably.Additionally, reference to “lipids” also includes “alkenones”.

In certain embodiments, the subject methods make use of certain speciesof algae which are capable of producing lipids. In a specificembodiment, the subject methods employ algae species which producealkenones, a class of lipids. Alkenes, alkenoates, and otherpolyunsaturated long-chain alkenones (PULCA), typically comprise 35 to40 carbons and methyl or ethyl ketones, although 37 and 38 carbons aregenerally the most dominant. Certain algae species (e.g. Isochrysisgalbana, Isochrysis litoralis, Isochrysis maritima, Emiliania huxleyi,and Gephyrocapsa oceanica) produce PULCA and package them intocytoplasmic vesicles or lipid bodies. The amount of these lipid bodiesmay change in response to various growth conditions. For example, theselipid bodies may increase under nutrient limitation, stationary phase,light changes, or temperature changes. On the other hand, these lipidbodies may decrease under prolonged darkness or too low temperatures.

Lipid-producing algae can include a wide variety of algae. The mostcommon lipid-producing algae can generally include, or consistessentially of, haptophytes (prymnesiophytes), diatoms(bacillariophytes), green algae (chlorophytes), blue-green algae(cyanophytes), and golden-brown algae (chrysophytes). Specificnon-limiting examples of haptophytes include Isochrysis, Pleurochrysis,Coccolithus, Chrysochromulina, Prymnesium, Chrysotila, Dicrateria,Emiliania, and Gephyrocapsa. Specific non-limiting examples ofbacillariophytes capable of lipid production include the generaAmphipleura, Amphora, Chaetoceros, Cyclotella, Cymbella, Fragilaria,Hantzschia, Navicula, Nitzschia, Phaeodactylum, and Thalassiosira.Specific non-limiting examples of chlorophytes capable of lipidproduction include Ankistrodesmus, Botryococcus, Chlorella,Chlorococcum, Dunaliella, Monoraphidium, Oocystis, Scenedesmus, andTetraselmis. In one aspect, the chlorophytes can be Chlorella orDunaliella. Specific non-limiting examples of cyanophytes capable oflipid production include Oscillatoria and Synechococcus. A specificexample of chrysophytes capable of lipid production includes Boekelovia.

In some embodiments, the subject methods employ an alkenone-producingalga, for example, a species of Haptophyceae and a member of the classof Prymnesiophyceae, the Isochrysis family, which includes, but is notlimited to, Isochrysis litoralis, Isochrysis maritime, Isochrysisgalbana, Isochrysis sp. T-Iso, and Isochrysis sp. C-Iso. Other examplesof alkenone-producing algae from the Emiliania family and theGephyrocapsa family include Emiliania huxleyi and Gephyrocapsa oceanica.For the co-production of biodiesel, alkenone-derived biofuels, andbiomass-derived co-products, many of species of algae such as Odontellaare not appropriate as alkenones are only naturally produced in thePrymnesiophyceae class of algae species. Other species would requiregenetic manipulation to induce the production of alkenones which may beconsidered and employed by the inventive methods.

In certain aspects, the lipid-producing algae (e.g. alkenone-producingalgae) can have a lipid content greater than about 20%, and preferablygreater than about 30% by weight of the algae. Currently known speciescontain a practical maximum lipid content of about 40% by weight,although levels as high as 60% have been shown, and strains developed ordiscovered in the future may achieve practical maximums higher than 40%.Such species would certainly be useful in connection with the presentinvention. In some embodiments, the subject methods are used to measurealkenone content of alkenone-containing species in order to select fornew algae species capable of producing high levels of lipids (e.g.alkenones). In some embodiments, the content of lipids is at least 20%,at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, atleast 80%, or at least 90% by weight of the algae.

In some embodiments, the alkenone-producing algae contain at least 3%alkenones 9 (w/w) relative to the starting dry algal culture 1. Inanother embodiment, the alkenone-producing algae comprises at least 5%,at least 7%, at least 10%, or even at least 20% alkenones 9 (w/w)relative to the starting dry culture 1. In one embodiment, analkenone-producing algal species is produced by in vitro or in vivoselection and contains at least 5% alkenones by weight. In someembodiments, the concentrations of alkenones 9 contained in thelipid-rich fraction 7 is at least 10%, at least 20%, at least 30%, atleast 40%, at least 50%, at least 60%, or at least 80% (w/w).

In certain aspects, the subject methods may include a combination of aneffective amount of two or more algae species in order to maximizebenefits (e.g. achieving optimal production of lipids includingalkenones).

In other aspects, the subject methods are directed towards a particularalgae species, while foreign species are preferably minimized and keptbelow an amount which would detrimentally affect yields of desiredlipids (e.g. alkenones). Undesirable algae species can be controlledand/or eliminated using any number of techniques. For example, carefulcontrol of the growth environment can reduce introduction of foreignspecies. Alternatively, or in addition to other techniques, a virusselectively chosen to specifically target only the foreign species canbe introduced into the growth reservoirs in an amount which is effectiveto reduce and/or eliminate the foreign species. An appropriate virus canbe readily identified using conventional techniques. For example, asample of the foreign algae will most often include small amounts of avirus which targets the foreign algae. This virus can be isolated andgrown in order to produce amounts which would effectively control oreliminate the foreign algae population among the more desirablelipid-producing algae.

In other embodiments, lipid-producing algae may be virally infected tobenefit the outcome and isolation of specific compounds such asalkenones 9 or co-products 16 (i.e. products derived from the biomass)derived from the inventive methods. The host algae may be induced by theviral components to serve as a platform for producing desired compounds.In some embodiments, the lipid or other compound composition changesover the course of infection. Such a viral infection may be employed toalter the alkenone unsaturation profile or to ultimately fine-tune thealkenone derivatives 12 obtained in the subject methods. In other cases,the viral infection may increase one or more types of lipids 7 and/oralkenones 9 to boost extraction yields. In another case, the viralinfection reduces undesired compounds which may reduce extractionyields.

In other embodiments with respect Bidle et al. U.S. Pat. No. 8,557,514incorporated by reference, the viral infection inhibits apoptoticpathways to increase lipids to produce higher yields of alkenones 9 andthus their subsequent derivatives 12. Other embodiments increaseproduction of carotenoids and/or additional co-products 16 that may beisolated through the biomass isolation process 13 in response to viralinfection. Furthermore, in other embodiments, the virally-infected algaeis induced to undergo apoptosis to release the cellular contents (e.g.lipids 7, alkenones 9, carotenoids, co-products 16, etc.), allowing theextraction processes to proceed more efficiently.

In some embodiments, the algae has been modified to alter thecomposition of desired compounds or traits thereof by chemical orgenetic manipulation (e.g. drug treatment, recombinant DNA, geneticengineering, transgenes, gene knockdown/knockout, nucleartransformation, gene transfer via bacteria, electroporation) such aslipid content, alkenone content, carotenoid content, fucoxanthincontent, photosynthetic rate, growth rate, gene expression, proteinexpression, etc. as a means to create a strain or strains capable ofproducing high levels of these desired compounds. In some embodiments,an alga strain is genetically modified to produce a higher lipid and/oralkenone content than an unmodified strain, resulting in analkenone-enriched strain.

In some embodiments, genetic material is introduced into a strain ofalgae to increase lipid and alkenone levels. The alga strain istransfected with a plasmid or plasmids containing constitutively activepromoters, transcription factors (e.g. VP16), or possibly enhancerregions that drive and increase the gene expression and protein levelsof other genes involved in the production, use, and/or storage oflipids, alkenones, fatty acids, or other desired algae compounds.Non-limiting examples of promoters that may be used are the Rubiscosmall subunit (RbcS2), ubiquitin (Ubil), cauliflower mosaic virus(CaMV35S), Cytomegalovirus (CMV), modified Cytomegalovirus enhancer withthe beta-actin promoter (CAG), and simian virus 40 (SV40). In anotherembodiment, the alga strain is transfected with a plasmid or plasmidscontaining constitutively repressive promoters or transcription factors(e.g. Engrailed) that decrease the gene expression and protein levels ofother genes involved in the production, use, and/or storage of lipids,alkenones, fatty acids, or other desired algae compounds. Genes ofinterest may include, but are not limited to, enzymes involved in lipidbiosynthesis, fatty acid modifying genes (e.g. desaturases,thioesterases), energy utilization genes, etc. In a particularembodiment an alkenone-rich algal species is transfected with one ormore genes providing resistance to a toxin (e.g. antibiotic orantiviral), and the entire culture population is exposed to the toxinresulting in a highly enriched alkenone-producing algal population. Inanother embodiment, alkenone-producing cells are transfected with areporter gene (e.g. green fluorescent protein) linked to a promoter fora marker of enzyme or protein expression important in alkenone synthesisor metabolism, to identify cells producing high levels of alkenones.Useful such promoters include the promoters for fatty acid unsaturase,fatty acid synthetase, acetyl-CoA carboxylase, glucokinase, pyruvatekinase, glycerol-3-phosphate acyltransferase, triacylglycerol lipase,monoacylglycerol lipase, as well as other synthetases, carboxylases,acyltransferases, dehydrogenases, lipases, and kinases associated withfatty acid or lipid synthesis or enhancer regions of said genes.

In other embodiments, a transgenic alga strain (i.e. strain withexogenous genetic material incorporated into the endogenous alga geneticmaterial) is developed. In additional embodiments, the transgenic algastrain is further modified by the transfection of plasmids to createstrains capable of producing even higher levels of the desiredcompounds. In some embodiment, nuclear transformation, gene transfer, orelectroporation is utilized to incorporate transgenes into alga straingenome.

In other embodiments, specific genes are knocked out or knocked down(i.e. no or reduced gene expression) using genome editing techniques(i.e. TALENs (transcription activator-like effector nucleases),CRISPR/Cas (clustered regularly interspaced short palindromicrepeats/CRISPR-associated genes), morpholinos, antisense oligos). Onecase uses TALENs to directly target the gene or genes of interest;another case utilizes the CRISPR/Cas gene editing technique to targetthe gene or genes of interest. Suitable targets for reduction ofexpression include but are not limited to, lipid storage genes, lipiddegradation genes, etc. In one embodiment, a lipase (a lipid-reducingenzyme) gene is knocked out or gene expression is reduced to allowincreased storage of lipids, alkenones, fatty acids, and/or otherbiofuel relevant compounds.

The algae may also be identified and selected for desired traitsmanually without the introduction of genetic material. In someembodiments, the alga strain is screened and selected for higher levelsof compounds (e.g. lipids, alkenone, carotenoids, fucoxanthin, etc.)than naturally present in algae without selection. In other embodiments,the algae are subjected to exposure of drugs, mutagens, or otherchemicals to alter the lipid, alkenone, and/or co-product contents.

Culturing Algae

In accordance with the present invention, the algae can be grown inreactors or reservoir structures, such as ponds, troughs, vats, ortubes, which are protected from the external environment and havecontrolled temperatures, atmospheres, and other conditions. Optionally,algae growth reservoirs can include a carbon dioxide source and acirculating mechanism configured to circulate alkenone-producing algaewithin the algae growth reservoirs. One way to achieve large surfacegrowth areas is in large ponds or in a captive marine environment. Inone embodiment, a raceway pond can be used as an algae growth reservoirin which the algae is grown in shallow circulating ponds with constantmovement around the raceway and constant extraction or skimming off ofmature algae. Other examples of growth environments or reservoirsinclude bioreactors.

It is also known that certain species of algae are much more prolific inthe production of lipids than others. However, these species may besusceptible to predation or displacement by native or volunteer specieswhich exist naturally in the environment where the growth reservoir islocated. Moreover, in most locations, temperatures may reach extremes ofheat or cold which could damage or at least retard the growth of thealgae. As such, some form of protection is usually desirable for thechosen algae species. In certain embodiments, low-cost greenhouses canbe built over the raceway ponds. These greenhouses can have enoughintegrity to maintain a positive pressure with airlocks, filtration, andtemperature control. This integrity can prevent the entrance of wildalgae and can maintain desired conditions for the algae crop.

In certain embodiments, the subject methods contemplate culturing analkenone-producing alga under a growth condition sufficient to producealkenones within the alga. Optionally, the growth conditions forculturing the alga may include growing the alga in a stationary growthphase, growing the alga under a high or low temperature, growing thealga in the presence of sufficient light (e.g. sunlight, artificiallight, dim light, low light intensity, high light intensity, light >12hr/day), growing the alga under a stress, or a combination thereof.Non-limiting examples of suitable stress include nutrient deprivation(e.g. nitrogen, phosphorous, and/or silicon), injection of a reactiveoxygen source (e.g. ozone or peroxide), viral, bacterial, or fungalinfection, and/or chemical additives. The underlying theory is that thealgae, under stress, store up energy in the compact form of lipids andalkenones by extracting carbon and energy from the available nutrientsin preparation for possible long-term harsh conditions. In someembodiments, algae are deprived of nitrogen, phosphorus, silicon, or acombination of the three nutrients to increase the biosynthesis oflipids, fatty acids, and alkenones of 5%, 10%, 20%, 30%, 40%, 50%, andup to 80%.

In one embodiment, the algae is cultured in greenhouse ponds undersufficient lighting (e.g. natural sunlight, artificial light, dim light)in a culture medium of suitable quality, including nutrients, pH,salinity, and other chemical parameters, such as a modified F/2 media orsimilar media known to those in the art. The algae are often grown intemperatures ranging 10° C. to over 55° C., with optimal conditions near18° C. to 25° C. In some embodiments, the algae are grown intemperatures lower than 25° C., 20° C., 15° C., 10° C., or even lessthan 5° C. as a means to increase and/or alter the lipid content of thealgae and to produce higher levels of less saturated lipids (e.g.lipids, alkenones) wherein the less saturated lipids are used to producealkenone derivatives of a carbon number of 5 to 20. In otherembodiments, the algae are grown in temperatures greater than 10° C.,greater than 15° C., greater than 20° C., greater than 25° C., greaterthan 30° C., greater than 35° C., and sometimes greater than 55° C. toproduce more saturated lipids (e.g. lipids, alkenones) wherein the moresaturated lipids are used to produce alkenone derivatives containing 5to 20 carbon atoms. In some embodiments, the algae are grown intemperatures greater than 10° C., greater than 15° C., greater than 20°C., greater than 25° C., greater than 30° C., greater than 35° C.,greater than 40° C., greater than 45° C., greater than 50° C. or greaterthan 55° C.

In other embodiments, the algae are subjected to low light conditions(i.e. 2 to 15 μmol photons m⁻² s⁻¹) to increase specific lipid contents.In other embodiments, the algae are subjected to high light conditions(i.e. 15 up to 135 μmol photons m⁻² s⁻¹) to increase specific lipidcontents. In some cases, the algae are grown in continuous light; inother cases, the algae are grown under 12 h/12 h light and dark cycle asa means to produce higher levels of lipids. Additionally, the light anddark cycle may be changed to 14 h/10 h, 16 h/8 h, 18 h/6 h,respectively.

In other embodiments, the algae is obtained from a mariculture facility.Industrially farmed algae may provide the scale necessary to producebiofuel as promising sources of alternative energy and valuableco-products.

Algae may be harvested in multiple ways. In one approach, algae areharvested by concentration (e.g. filtration) and dehydration. In aspecific embodiment, a lyophilized (e.g. freeze-dried) algal sample isobtained for further processing as described below. Other embodiments,the algae is dried or dehydrated by evaporation with or without theaddition of solvents by vacuum drying, drum drying, hot air exposure(e.g. convective or direct drying), dielectric drying, supercriticaldrying, natural air drying, or other suitable method to produce a sampleremoved of fluid (e.g. non-aqueous sample) to produce the dry culture 1.In other embodiments, a wet algal biomass sample is processed.Furthermore, the algal sample may be lysed, crushed, or ground, eitherprior or subsequent to dehydration, although various embodiments do notrequire the algal sample to be in the powder form. Additionally, thecrushing of algae using a high-pressured method of homogenizing theculture sample may not be appropriate for the production of biodiesel 6and biofuel 12 in parallel with the production of co-products 16 fromthe biomass 3.

Recovery of Lipids from the Algae

The subject methods relate to recovery of lipids (e.g. alkenones) fromthe algae. Algae store lipids inside the cell body, sometimes but notalways, in vesicles. The lipids can be recovered in various ways,including through the use of solvent extractions, either alone or in thepresence of heat, pressure, and/or depolymerization processes (such asbiologically breaking the walls of the algal cell and/or oil vesicles,if present, to release the lipids from the algae). In certainembodiments, at least one of three types of biological agents may beused to release algae energy stores, for example, enzymes such ascellulase or glycoproteinase, structured enzyme arrays, or a system suchas a cellulosome, a viral agent, or a combination thereof. A cellulaseis an enzyme that breaks down cellulose, especially in the wallstructures, and a cellulosome is an array or sequence of enzymes orcellulases which is more effective and faster than a single enzyme orcellulase. In both cases, the enzymes break down the cell wall and/orlipid vesicles and release lipids from the cell. Cellulases used forthis purpose may be derived from fungi, bacteria, or yeast. Non-limitingexamples of each include cellulase produced by fungus Trichoderma reeseiand many genetic variations of this fungus, cellulase produced bybacteria genus Celluiomonas, and cellulase produced by yeast genusTrichosporon. A glycoproteinase provides the same function as acellulase, but is more effective on the cell walls of microalgae, manyof which have a structure more dependent on glycoproteins thancellulose.

In addition, a large number of viruses exist which invade and rupturealgae cells, and can thereby release the contents of the cell, inparticular stored lipids. Such viruses are an integral part of the algalecosystem, and many of the viruses are specific to a single type ofalgae. Specific examples of such viruses include the chlorella virusPBCV-1 (Paramecium Bursaria Chlorella Virus) which is specific tocertain Chlorella algae, and cyanophages such as SM-1, P-60, and AS-Ispecific to the blue-green algae Synechococcus. The particular virusselected will depend on the particular species of algae to be used inthe growth process. One aspect of the present invention is the use ofsuch a virus to rupture the algae so that lipids inside the algae cellwall can be recovered. In another detailed aspect of the presentinvention, a mixture of biological agents can be used to rupture thealgal cell wall and/or lipid vesicles.

Mechanical crushing, for example, an expeller or press, a chemicalsolvent recovery step, supercritical fluid extraction, or the like canalso be useful in extracting the lipids from lipid vesicles of thealgae. Alternatively, mechanical approaches can be used in combinationwith biological agents in order to improve reaction rates and/orseparation of materials.

In some embodiments, algal compounds (e.g. lipids, alkenones,co-products) are extracted from the algal culture 1 (i.e. the dry algalsample prior to extraction) using chemical solvents. Extraction oflipids 7, alkenones 9, and co-products 16 of varying polarities andsolubilities can be improved by use of a particular solvent or mixtureof solvents. Preferred solvents and solvent mixtures may vary based onthe solubility of the desired extracted compound.

The first extraction 2 (i.e. extraction with solvent #1) is performed asa means to isolate the biofuel oil 4 containing the fatty acids, lipids,alkenones, and related compounds of the algal culture 1 from the algalbiomass 3. It is important to note that this first extraction withsolvent #1 2 is a selective extraction process that enhances thesubsequent extractions downstream (i.e. extraction with solvent #2 8,extraction with solvent #3 13). In one embodiment, the algae 1 isextracted with solvent #1 2 to produce a biofuel oil 4 containingalkenones 9 and a biomass 3 containing co-products 16. In anotherembodiment, the algae 1 is extracted with polar solvent #1 2 to producea biofuel oil 4 containing alkenones 9 and a biomass 3 containingco-products 16. In an additional embodiment, the algae 1 is extracted ina non-aqueous (i.e. water-free) reaction with polar solvent #1 2 toproduce a biofuel oil 4 containing alkenones 9 and a biomass 3containing co-products 16. In some embodiments, non-polar solvents aregenerally used (e.g. hydrocarbons 1 to 22 carbons in length, benzene,toluene, cyclohexane, chloroform, ether, 1,4-dioxane, neutral ornon-ionic surfactants). In one embodiment, the algal culture 1 is firstextracted using n-hexanes. Other embodiments use other hydrocarbons suchas pentane, cyclopentane, iso-hexane, n-heptane, iso-heptane, octane,iso-octane, benzene, or toluene. Some embodiments use a combination ofnon-polar solvents.

Extraction with solvent #1 2 releases many of the algal compounds fromthe algae culture 1, which can be recovered or separated from thenon-aqueous slurry of algae debris material (e.g. cellular residue,enzymes, by-products, etc.) referred to as the algal biomass 3. This canbe done by filtration, sedimentation, or centrifugation, withcentrifugation often being preferred. In one embodiment, the dehydratedalgae culture 1 is mixed with solvent #1 2 and introduced into a Soxhletor equivalent extraction apparatus to extract the biofuel oil 4 from thealgal culture 1.

The recovered biofuel oil 4 comprising fatty acid-rich fractions (e.g.fatty acids, fatty acid derivatives) and lipid-rich fractions can becollected and directed to a specific conversion processes as describedin more detail below. Product fractions from the extraction with solvent#1 2 are approximately 60% free fatty acids and 40% lipids, howeverthese ratios may differ up to a 10-20% range. In some embodiments, thelipid content may be 50%, may be 60%, may be 70%, or may be 80% byweight relative to the starting culture 1 using a genetically modifiedalgal source. The algal biomass 3 may also be collected and saved for aseparate processing procedure 13 (i.e. extraction with solvent #3)and/or other process as described below for recovery of valuableco-products 16.

Further chemical modifications of the biofuel oil 4, such asesterification, acid-catalyzed esterification, and transesterification,may be employed as a means to produce fatty acid methyl esters (FAMEs)6, lipids/neutral lipids 7, and/or other by-products such as soap andglycerol. The esterification reaction 5 is conducted using an alcohol,acid or base catalyst, and potentially other reagents like chloroform.In some embodiments, esterification 5 may entail the use of suitablereagents including alcohols comprising a number of carbon atoms rangingfrom 1 to 20 such as methanol, ethanol, propanol, etc., and an acid orbase catalyst(s) such as sulfuric acid, hydrochloric acid, potassiumhydroxide, sodium hydroxide, sodium methoxide, or other appropriatereagents. In another embodiment, the reaction is carried out in thepresence of a lipase enzyme as a means to enhance the efficiency of thereaction. In other embodiments, the esterification reaction 5 isconducted to allow removal of fatty acids, fatty acid derivatives, andFAMEs 6 to facilitate the purification of lipids 7 and/or the alkenones9.

Some cases may include spiking the biofuel oil 4 with an internalstandard such as ethyl nonadecanoate for quantification of reactionefficiency or chromatography analyses. Other cases involve spiking withpurified alkenones 9 with an internal standard.

In many embodiments of the invention, the source alga endogenouslyproduces fatty acids and FAMEs. In some instances then, free fatty acidsand/or FAMEs will be present in the biomass 3, and/or biofueloil-containing fractions 4. In a few preparations, alkenones 9 will beprepared without separating or otherwise removing the endogenous FAMEs,and without the addition of exogenous FAMEs to any fraction(s). In caseswhere endogenous FAMEs are present in one or more fractions, they willbe present at a concentration (wt/v) of less than 80% (4:1) and morepreferably less than 50% (1:1) and most preferably less than 20% (1:4),or even less than 15, 10 or 5%. In one embodiment, fatty acids and fattyacid derivatives including FAMEs 6 are separated from the alkenones 9and discarded. In another embodiment, the neutral lipids 7 are isolatedfrom the FAMEs 6 as a means to produce a lipid-rich fractionsubstantially free of FAMEs. This lipid-rich fraction may be furthermodified to produce alkenone derivatives 12 as described below.

Conversions of Algal Lipids to Alkenone Derivatives

In certain embodiments, the subject methods relate to converting algallipids (e.g. lipids 7, alkenones 9, lipid-rich fraction 7) into alkenonederivatives 12 (i.e. products derived from alkenones or chemicalmodification of alkenones). By one method, the alkenones 9 are firstpurified from the other lipids 10 to produce substantially purealkenones 9 (i.e. a chemical that is chemically pure or analyticallypure wherein the chemical has a purity greater than 70%, greater than75%, greater than 80%, greater than 85%, greater than 90%, greater than95%, greater than 98%, or greater than 99%.). In some embodiments, thelipid-rich fraction 7 is chemically modified to separate alkenones 9from other lipids 10 which may be accomplished by several methods suchas purification with a solvent or solvents and recrystallization,chromatography, or other suitable process. Another method does notrequire the alkenones 9 to be first purified from the lipid-richfraction 7, thus allowing the lipid-rich fraction 7 to be chemicallymodified to produce alkenone derivatives 12. Additionally, some methodsmay even be employed to allow a mixture of FAMEs 6, lipids 7, alkenones9, and other inherent derivatives to be chemically modified to producealkenone derivatives 12.

Most cases prefer a water-free extraction of alkenones 9 (i.e. noexogenous water added). In some embodiments of lipid/alkenonepurification 8, the alkenones 9 are dissolved in a minimal amount ofsolvent (i.e. low volume), flushed though a filter (e.g. silica gelmesh, column), and purified with the same solvent or one of similarproperties wherein the suitable solvent or solvents capable ofsolubilizing alkenones are primarily polar or have partial polarproperties (e.g. chloromethane, dichloromethane, dichloroethane,tetrahydrofuran, dimethylformamide, acetonitrile, nitromethane,propylene carbonate, formic acid, butanol, isopropanol,methyltetrahydrofuran, trifluoromethylbenzene, ethyl acetate, ethylether, acetone, dimethyl sulfoxide, alcohols, acetic acid, esters,ethers) now referred to as solvent #2 8. In one embodiment, the polarextraction with solvent #2 8 is performed with dichloromethane, and thepurified alkenones are recrystallized with either dichloromethane orn-hexanes. In another embodiment, this reaction 8 proceeds using toluene(PhMe). In one embodiment, the alkenones are extracted usingmethyltetrahydrofuran. In another embodiment, the alkenones 9 areisolated using acetonitrile. Additionally, dimethyl sulfoxide may beused to extract the alkenones 9.

In another embodiment, the alkenones 9 are purified from other lipids 10by using a non-polar solvent or solvents (e.g. alkanes, n-hexanes,benzene, toluene, 1,4-dioxane, chloroform, ether). In both cases ofpolar and non-polar solvent use, the solvent(s) #2 8 may be cooled orevaporated to allow the alkenones 9 to recrystallize to produce asubstantially pure alkenone solid material 9. In some embodiments, thealkenones 9 extracted and are then recrystallized using n-hexanes,methyltetrahydrofuran, tetrahydrofuran, dimethyl ether, diethyl ether,methyl-tert-butyl ether, dichloromethane, acetonitrile, dichloromethane,an alkane compound of 1 to 10 carbons, benzene, or other suitable listedsolvent or a combination thereof. In certain embodiments, extractionwith solvent #2 generally results in an yield of 20%, a yield of 30%, ayield of 40%, a yield of 50%, a yield of 60%, or up to a yield of 80% ofpurified alkenones 9 (w/w) from the neutral lipids 7 or a total alkenonecontent at least 3-5% up to 20% (w/w) of the Isochrysis dry culture 1.In other embodiments, the substantially pure alkenones 9 are of a puritygreater than 50%, greater than 60%, greater than 70%, greater than 80%,greater than 90%, or even greater than 95%.

The purified alkenones 9 may be analyzed by gas chromatography andcompared to a set of standards to determine the composition of thealkenones. In some cases, analysis reveals the presence of C37:3, C37:2,C38:2, and C38:3 alkenones along with small amounts of the C39:3 andC39:2 with the most abundant being the methyl 37:3 (where C#:# refers tothe number of carbon atoms:number of double bonds). In one embodiment, acomplete set of alkenones 9 extracted from the dry culture 1 may rangefrom 35-42 carbons with 2-3 double bonds and methyl or ethyl ketones.

The purified alkenones 9 may be further modified to produce alkenonederivatives 12. Suitable methods allow for the carbon-carbon bonds (e.g.double bonds, single bonds) present in the alkenones 9 to be brokenand/or reorganized to produce hydrocarbons (e.g. alkenes, alkanes) andorganic hydrocarbon products (e.g. ketones, aldehydes, carboxylic acids,esters, amides, amines, etc.) of a size compatible for biofuel. In someembodiments, the alkenones 9 are converted to biofuel 12 in thehydrocarbon range of 2 to 42 carbons. In some embodiments, the subjectmethods produce a composition of alkenone derivatives comprising 5 to 20carbon atoms. In other embodiments, alkenone derivatives are producedcomprising 20 to 30 carbon atoms. In other embodiments, the methodsproduce alkenone derivatives comprising more than 30 carbon atoms. Inone embodiment, the subject methods produce a composition of alkenonederivative mixture 12 comprising a C5-C22 hydrocarbon mixture(kerosene/jet fuel boiling range) and under certain conditions,predominantly 8-decen-2-one (C10), 2,9-undecadiene (C12), and2-heptadecene (C17) as both cis- and trans-isomers.

One process for converting alkenones 9 (purified or mixed with otherlipids 10 and/or FAMEs 6) to hydrocarbons is catalytic hydroprocessing,pyrolyzing, or cracking Catalytic hydroprocessing technology is wellknown in the art of petroleum refining and generally refers toconverting at least large hydrocarbon molecules to smaller hydrocarbonmolecules by breaking at least one carbon-carbon bond. However, crackingmethods tend to be less selective in location of carbon bond breakingand produce a wider variety of derivatives than other methods such ascross metathesis-type reactions. In some cases, a more diverse mixtureof alkenone derivatives 12 is desired; other cases require only specificsized alkenone derivatives 12 to be produced. In cases wherehydroprocessing is utilized, the resulting alkenone derivatives are mostoften a various mixture of smaller hydrocarbon fragments and polymerscomprising acrylic acids, acrylic esters, alkenes, vinyl chloride, vinylacetate, diacids, diamines, diols, plastics, and/or lactic acid. Thesealkenone derivatives 12 or mixtures of derivatives may not beappropriate for use as a co-produced biofuel source particularly for theuse of jet fuel/kerosene biofuel.

In some embodiments, the purified alkenones 9 are converted to alkenonederivatives 12 through a different and separate process thanhydroprocessing using a type of cross metathesis reaction 11 (e.g. crossmetathesis, olefin metathesis, alkenolysis) in the presence of acatalyst to produce alkenone derivatives 12 with olefin functionalgroups. Metathesis is a catalytic reaction, generally known in the artthat involves the interchange of alkylidene units among compoundscontaining one or more double bonds (e.g. olefinic compounds) via theformation and cleavage of the carbon-carbon double bonds. Metathesis mayoccur between two like molecules (often referred to as self-metathesis)and/or it may occur between two different molecules (often referred toas cross metathesis). In the broad sense, the cross metathesis-typereaction 11 involves the rearrangement of carbon double bonds to produceproducts with olefin functional groups in the presence of a solvent andcatalyst. More specifically, cross metathesis reactions occur with morepredictable alkene products than hydroprocessing and can produce alkeneproducts derived from alkenones in the necessary size range for uses asjet fuel or kerosene biofuel.

Suitable catalysts include organometallic compounds (e.g. molybdenum-,tungsten-, mercury-, ruthenium-based compounds) or of the like. Suitablesolvents comprise alkanes with 1 to 32 carbons (e.g. ethane, butane,pentane, etc.), dichloromethane, dichloroethane, chloroform, benzene,toluene, methyl-tert-butyl ether, and acetic acid and related compounds(e.g. isopropyl acetate, ethyl acetate) although alkenes are preferredsolvents in the processing of the alkenones 9. Other present reagents orcompounds may include alkenes with 2 to 32 carbons (e.g. ethene,propene, butene, etc.), methyl stearate, ethyl vinyl ether, acrylates,or suitable substitutes.

In one aspect, the cross metathesis-type (i.e. alkenolysis) reaction 11is butenolysis using a butene reagent. Suitable solvents includechloroform, dichloromethane, chloromethane, and toluene (PhMe) howeverother solvents capable of efficiently solubilizing the alkenones may besubstituted or even added. One butene reagent which may be used is2-butene which may be in the cis- or trans-chemical orientation,although other embodiments utilize 1-butene, and is preferably added tothe reaction in excess. Other reactions such as ethenolysis utilize anethene reagent (i.e. ethenolysis). In some embodiments, the crossmetathesis reaction may be repeated 1 or more times to achieve the mostefficient conversion of alkenones 9 to alkenone derivatives 12.

Although this particular type of reaction may be conducted at a range oftemperatures from −20° C. up to 100° C., some cases achieve optimumresults temperatures ranging from −5° C. to 4° C. or room temperature20° C. to 30° C. In the case of low temperature reactions, arefrigerated space, ice bath, or other suitable means to chill thereaction may be used. For adequate conversion of alkenones 9 to alkenonederivatives 12, the cross metathesis-type reaction may require reactiontime of 1, 10, 20, 30, or 40 minutes and may take as long as 1 hour, aslong as 2 hours, as long as 3 hours, as long as 4 hours, as long as 5hours, as long as 6 hours, as long as 7 hours, as long as 8 hours, aslong as 9 hours, as long as 10 hours, as long as 11 hours, as long as 12hours, as long as 13 hours, as long as 14 hours, as long as 15 hours, aslong as 16 hours, as long as 17 hours, or as long as 18 hours dependingon solvents, alkene reagents, alkenone concentration, and catalystsemployed. Non-limiting examples are shown in FIG. 15 which providesadditional embodiments and associated conditions. In some embodiments,following desired completion of the alkenone conversion, ethyl vinylether may be added to quench the reaction.

In certain embodiments, the alkenone derivatives 12 produced by crossmetathesis are predominantly 8-decen-2-one, 2-heptadecene, and2,9-undecadiene. Often, the percentages of 8-decen-2-one, 2-heptadecene,and 2,9-undecadiene present after the reaction are in the range of atleast 10%, 20%, and 40%, respectively. In one case, the ratio of crossmetathesis products 8-decen-2-one, 2-heptadecene, and 2,9-undecadiene bygas chromatography analysis is typically 1:2:2.5, respectively. Products8-decen-2-one and 2,9-undecadiene are often present in a trans:cischemical orientation of 3:1 to 4:1, respectively. Other alkenonederivatives may comprise 15-heptadecen-2-one, 9-undecen-3-one,16-octadecen-3-one, and 2-nonadecene along with trace other products.

The long chains of carbon in the alkenones 9 produced by algae (e.g. 30to 42 carbons) can be used to produce a wider range of biofuels orlubricating oils than those derived from glycerides (e.g. 5 to 22carbons). In another embodiment, unpurified alkenones comprising amixture of alkenones 9, lipids 10, FAMEs 6, etc. are converted tohydrocarbons without separating the FAMEs 6 from the lipids 7 prior tohydroprocessing or cross metathesis-type reactions 11. Furthermore,another embodiment allows the unpurified alkenones comprising only thelipid-rich fraction 7 to undergo cross metathesis 11 to produce alkenonederivatives 12.

In certain embodiments, the subject methods comprise converting algalalkenones 9 into a liquid fuel such as diesel or gasoline. In otherembodiments, the subject methods comprise converting algal alkenones 9into a gaseous fuel, such as a syngas (a mixture of CO and H2) and/or asynthetic hydrocarbon gas (e.g. methane, propane, and butane).

In certain embodiments, the subject methods comprise converting the longchains of the alkenones 9 into methane and supercritical carbon dioxideby technologies that use high temperature liquid metal chemistry. Suchtechnologies are known in the art. For example, algal biomass 3 may beconverted into methane via hydrothermal processes. Optionally, growingof algae and hydrothermal processing of algae culture 1 may be coupledinto a continuous process. It may be possible to introduce the algalculture 1 directly into a reactor for hydrothermal gasification. Thus,this approach may allow the use of the algae cells 1, directly withoutfirst extracting the algae biofuel oil 4, for the production ofhydrocarbons or polymers, eliminating several costly steps such assolvent extraction.

Analysis and quantification of the resulting alkenone derivativecomposition 12 and reaction efficiency may utilize ¹H nuclear magneticresonance (¹H NMR) spectroscopy using a solvent such as CDCl₃ or of thelike. One-dimensional gas chromatography with flame ionization detection(GF-FID), two-dimensional gas chromatography with flame ionizationdetection (GC×GC-FID), time of flight mass spectrometry (GC×GC-TOF), andgas chromatography-mass spectrometry (GC-MS) may also be applied forfurther reaction analysis.

Recovery of Commercially Valuable Co-Products

In addition to the production of biodiesel 6, biofuel 12, and otheralkenone derivatives 12, a parallel (i.e. simultaneous, coordinated)extraction method may be employed to isolate other commercially valuableco-products (e.g. products derived from the algae biomass 3, productsproduced by chemical modification of the biomass 3, of which havemonetary value) from the algal culture 1, more specifically the algalbiomass 3 (i.e. the residual algal debris material of the initialextraction 2). In particular, this complementary method utilizes thewaste-stream normally discarded in the production of biodiesel 6 toproduce valuable co-products 16 without the disruption or alteration ofthe algae-to-biodiesel/algae-to-alkenone derivatives processes. Uponpreparing the algae culture 1 for the extraction with solvent #1 2 toextract the biofuel oil 4, the algal biomass 3 may be separated andfurther processed through an additional method described below.

In one embodiment, the biofuel oil 4 is extracted from a non-aqueousalgal culture slurry 2 in the presence of a non-polar solvent #1.Solvent #1 2 may then be evaporated, and the biofuel oil 4 may beisolated using a filter, membrane, separatory funnel, extractionthimble, or similar means to remove the biofuel oil 4 from the algalbiomass 3. In some cases, an extraction apparatus such as a Soxhletextractor may be used; other cases do not require the use of a Soxhletextractor or comparable apparatus. As mentioned above, the initialnon-polar extraction with solvent #1 2 selectively solubilizes andremoves alkenones 9 from the algal biomass 3 which results in anenriched and more purified co-product-containing biomass 3 substantiallyfree of alkenones 9 (i.e. at least 70%, 80%, 90%, or greater than 95%free of alkenones). A polar extraction 13 with a solvent such as ethanolwithout a prior non-polar extraction 2 would non-selectively pull down awider range of compounds (i.e. contaminants) and would requireadditional selective partitioning with water to achieve the sameresults.

The algal biomass 3 (i.e. the biomass fraction) removed of the biofueloil 4 can be combined with one or more suitable solvents 13, nowreferred to as solvent #3, to further extract the biomass oil 14 (i.e.biomass oil fraction) containing the algal co-products 16. Such suitablesolvents may comprise polar solvents (e.g. chloromethane,dichloromethane, dichloroethane, tetrahydrofuran, methyltetrahydrofuran,ethyl acetate, acetone, dimethyl sulfoxide, alcohols, acetic acid,esters, ketones, amines, carboxylates, halogenated hydrocarbons),non-polar solvents (e.g. hydrocarbons 1 to 22 carbons in length,benzene, toluene, chloroform, dimethyl ether, n-hexanes, iso-hexanes),and surfactants although this extraction 13 is most often performed witha polar solvent. In one embodiment, a polar solvent 13, morespecifically an alcohol such as ethanol, is added to the algal biomass 3to release the biomass oil 14. In another embodiment, the polar solventmethanol is used to extract the biomass 3.

In embodiments of the extraction with solvent #3 13, the extraction isconducted in the dark or a minimal amount of light (e.g. dim light, nolight) to prevent decomposition or photo-oxidation. In some embodiments,the term “minimal amount of light” is 0 seconds, less than 5 seconds,less than 10 seconds, less than 15 seconds, less than 30 seconds, lessthan 1 minute, less than 2 minutes, less than 5 minutes, and up to lessthan 10 minutes. In another embodiment, the extraction may be carriedout in a certain spectrum of light such as red light or other specificlight range as to limit photo-oxidation. Other algal biomass extractions13 may not require dark conditions depending on the desired co-products16 to be isolated.

In order to effectively extract co-products 16, a proper ratio ofsolvent(s) 13 to algal biomass 3 (w/v) may be considered. In some cases,a ratio greater than 20:1 solvent/algal biomass is sufficient whileother cases may require higher concentrations of solvent more on theorder of greater than 30:1 or even 40:1. Other extractions may onlyeffectively work under a lower solvent/algal biomass ratio less than20:1, 10:1, 5:1, ranging down to 1:1.

Temperature and time are also of concern in the extraction ofco-products 16. While some co-product extractions 13 benefit fromproceeding below 45° C., 25° C., 10° C., 4° C. or even 0° C., otherextractions may be performed at higher temperatures greater than 25° C.,30° C., 40° C., or 45° C. Under certain parameters, extraction at 45° C.may not be suitable to prevent decomposition of the desired extractedco-products 16. Extraction time can also affect the resulting co-productyields 16, of which can vary from as little as 1 minute to more than 240minutes and possibly spanning overnight or over several days. In someembodiments, optimum yields are acquired only after extraction for atime period longer than 2 hours. In another embodiment, the biomass 3 isextracted for at least 10 minutes.

The subsequent biomass slurry with solvent #3 13 may be dried byevaporation using a rotary evaporator or other means (e.g. vacuumdrying, drum drying, hot air exposure (e.g. convective or directdrying), dielectric drying, supercritical drying, natural air drying,etc.) and subjected to filtering or like means to separate the fluidphase from the residual solid biomass material resulting in the isolatedbiomass oil 14.

In some cases, the biomass oil 14 may be further modified orfractionated to produce additional co-products 16. In one embodiment,the biomass oil 14 is fractionated by chromatography 15 (e.g. flashchromatography, high-performance liquid chromatography, liquidchromatography). Chemical standards such as a fucoxanthin standard maybe spiked into the biomass oil 14 as an internal reference forcomparison. The resulting fractions may be analyzed by ¹H NMRspectroscopy using a suitable solvent. Absorbance spectroscopy, highperformance liquid chromatography, or gas chromatography may be appliedfor additional analysis.

Suitable chromatography 15 solvents may include one or more n-hexanes,ethyl acetate, ether, acetone, toluene, petroleum ether,dichloromethane, methanol, hydrocarbons or of the like as well asspecific ratios of solvents to obtain optimum purified fractionproducts. In one embodiment, a mixture of n-hexanes and ethyl acetate isused in a ratio ranging from 1:1 to 10:1, respectively. Otherembodiments do not use an n-hexanes/acetone mixture or at least not in aratio 6:4, respectively.

One commercially valuable fraction that may be obtained through thismethod contains a carotenoid or carotenoids, particularly fucoxanthin 16(e.g. trans-fucoxanthin, cis-fucoxanthin, fucoxanthin-related compounds)which may be subjected to further purification if necessary. In oneembodiment, at least 50% up to 80% or even 90% of the total extractedfucoxanthin 16 is contained and obtained from the biomass oil 14.

In one embodiment wherein the 30 g of dry algal culture 1 is extractedwith n-hexanes as solvent #1 2, yields of biofuel oil 4 may be near 4-7g and further extraction of the biomass 3 with ethanol as solvent #3 mayisolate 2-5 g of biomass oil 14 from the biomass 3, producing yields of0.01 to 0.6 g of fucoxanthin 16. Furthermore, a 30 g dry culture 1extracted by solvent #2 2 and solvent #3 13 may yield an average totalfucoxanthin extract 16 from Isochrysis dry samples at least 5 mg/g, 10mg/g, 20 mg/g, 30 mg/g dry weight or 0.5%, 1%, 2%, 3% (w/w),respectively. Depending on the batch of starting culture, fucoxanthinyield may average 0.5%, 1%, and possibly up to 3%, 4%, or more than 5%(w/w) of the starting culture.

In another embodiment, a dry algae culture 1 of 50 g is extracted toproduce about 10 g of biofuel oil 4 and about 2 g of biomass oil 3 (5:1ratio, respectively). The biofuel oil 4 is further modified to produceapproximately 5.4 g of FAMEs 6 and 1.6 g of alkenones 9 (27:8 ratio,respectively). Modifying the biomass oil yields near 0.4 g offucoxanthin 16. In a parallel co-production of FAMEs 6, alkenones 9, andfucoxanthin 16, the extraction of a single batch of algae produces aratio of 27:8:1, respectively. In other embodiments, the yield of FAMEs6 may be closer to 2 g, 4 g, 8 g, or 9 g (ratio of 10:8, 20:8, 40:8, or45:8 FAMEs:alkenones). In some embodiments, yields of alkenones 9 are0.5 g, 1 g, 2 g, 4 g, and up to 6 g (ratio of 27:2.5, 27:5, 27:10,27:20, and 27:30 FAMEs:alkenones). In other embodiments, co-product ormore specifically fucoxanthin 16 extraction yields are near 0.01 g, 0.1g, 0.2 g, 0.4 g, 1 g, or 1.5 g (ratio of 0.2:32, 2:32, 4:32, 8:32,20:32, or 30:32 co-product:alkenones).

In some cases, it may be greatly important to produce both the cis andtrans isomers of fucoxanthin. Algae species of the Isochrysis familyproduce both isomers as compared to some algae which only produce oneisomer or very limited amounts of one isomer. Other cases may benefitfrom only producing the cis or the trans isomer of fucoxanthin dependingon the desired future use of the isolated compound.

Example 1

The following example describes a specific embodiment of the inventivemethod to produce alkenones and alkenone derivatives, which is includedto further illustrate certain aspects of the invention and are notintended to limit the invention.

Introduction

In preparation for a future 1-acre-sized bio-production site in CapeCod, Mass., USA (41° 33 05″ N, −70° 36 55″ W), we surveyed local speciescapable of sustainable growth and high production of FAMEs in the lowincidence of annual light availability and cool temperatures of theregion. One of our targeted algae was the coastal marine prymnesiophyteIsochrysis sp. including strains T-Iso and C-Iso. We were interested inIsochrysis sp. as they are rich in polyunsaturated fatty acids (PUFAs),can be grown both indoors and outdoors (D. Kaplan et al., CRC Press, FL,1986, pp. 147-198), have no cell walls, and are grown commercially formariculture feedstocks (P. Lavens and P. Sorgeloos, Manual on theproduction and use of live food for aquaculture, Fisheries TechnicalPaper 361, Food and Agriculture Organization of the United Nations,1996; M. Albentosa, et al. Aquaculture, 1996, 148, 11-23; C. T. Enright,et al., Journal of Experimental Marine Biology and Ecology, 1986, 96,1-13). Furthermore, this effort conforms to the future fuels strategyproposed by Inderwaldi and King stressing the importance of in-depthscientific analysis of short, medium, and long-term aspects of biofuelproduction (O. R. Inderwildi and D. A. King, Energy & EnvironmentalScience, 200, 2, 343-346).

Methods and Materials

1. Microalgal Species and Culture Conditions.

Two Isochrysis sp. strains “T-Iso” and “C-Iso” and the diatom,Thalassiosira weissflogii strain “TW” were sourced from the MilfordLaboratory Microalgal Culture Collection (Milford, Conn.). Additionalinformation on the “T-Iso” and “C-Iso” strains have been described indetail (G. H. Wikfors and G. W. Patterson, Aquaculture, 1994, 123,127-135). In this study, we included TW to highlight differences inlipid profiles of algae. Microalgae were cultured in 250 ml glassErlenmeyer flasks under 24 hour lighting (approximately 31 μmol. photonsm⁻² s⁻¹) and held on an oscillating shaker (100 rpm) at 19° C. StandardF/2 media was used for cultures with silica provided for the comparison“TW” strain. Microalgae were harvested by centrifuging at 4,000 rpm anddecanting the supernatant. The remaining algal pellet was freeze-dried.

2. Extraction of Algal Samples.

Freeze-dried algal biomass (10 to 50 g) were extracted with hexane. Theresultant lipid extract was spiked with an internal standard, ethylnonadecanoate, and transesterified under N₂ using 10% methanolic HCl inhexane (55° C.; 12 hours). We used ethyl nonadecanoate to check both thecompleteness of the transesterification reaction by monitoring theproduction of methyl nonadecanoate and using the latter forquantification purposes. The reaction products were extracted withhexane, reduced in volume, spiked with an external standard,n-heptadecane, and stored until analysis by the GC-FID.

3. Analysis by Gas Chromatography with Flame Ionization Detection(GC-FID).

We quantified FAMEs and alkenones in the esterified samples using aHewlett-Packard 5890 GC-FID. Compounds were separated on a glasscapillary column (J&W DB-1 MS, 30 m, 0.25 mm i.d., 0.25 μm filmthickness) with H2 carrier gas. FAMEs were identified with standardspurchased from Nu-Chek Prep (Elysian, Minn.) and Supelco (Bellefonte,Pa.). Alkenones were identified based on comparison to published elutionorder on gas chromatographic columns, their mass spectra, and mixturesharvested from cultures of Isochrysis sp. Methyl nonadecanoaterecoveries were always >90%. No ethyl nonadecanoate was observed in thesamples.

Example 2

The following example describes a specific embodiment of the inventivemethod to simultaneously produce alkenones and alkenone derivatives inparallel with the production of fucoxanthin, which is included tofurther illustrate certain aspects of the invention and are not intendedto limit the invention.

Introduction

The need for new energy supplies to meet a growing global demand and adesire for renewable, sustainable, and domestic feedstocks continues todrive much research aimed at investigating alternative energy sources.Recently, there has been a great resurgence of interest in algae as apotential biofuel feedstock; particularly for the production of liquidfuels such as biodiesel and other biomass-derived oils. Proposedbenefits include the avoidance of certain fuel vs. food controversiesand reportedly higher productivities when compared to traditionalagricultural crops. Criticisms of algal biofuel programs tend to focuson projected costs of the overall process, essentially echoing oneconclusion from Sheehan's report on the United States Department ofEnergy-sponsored Aquatic Species Program (ASP). The ASP was started in1978 for the purpose of investigating transportation fuel from algae andwas defunded in 1996 primarily because projected costs were in the rangeof $40-60 per barrel (42 gallons=159 L) compared to $18.46 for crudepetroleum at that time. While the cost of petroleum has increaseddramatically in recent years, critics remain who contend thatnonetheless algal biofuels will prove too costly. For instance in arecent perspective on microalgal transportation fuels, van Beilen arguesthat algae productivities do not surpass those of irrigated tropicalcrops and cultivating, harvesting and processing microalgae is simplytoo expensive. The author goes on to state that “only if the algalbiomass is a byproduct of . . . the production of high-value compoundssuch as astaxanthin or beta-carotene, commercially viable energyproduction from algal biomass might be feasible.” Many others includingChisti and Wijffels have stressed the importance of value addedco-products as a necessary component of algal biofuel production. TheUnited States Department of Energy (DOE) “National Algal BiofuelsTechnology Roadmap” goes on to identify valuable co-products as one ofthe key reasons for exploring algae as a source of biofuels.

Recently we have focused on Isochrysis as they produce a unique andpromising class of lipids known as long-chain alkenones. These compoundsare unlike the cis-unsaturated methylene interrupted fatty acidcomponents of triacylglycerols (TAGs) as they typically have two to fourtrans-alkenes occurring at 7-carbon intervals (FIG. 2). At colder growthtemperatures, alkenones are more highly polyunsaturated, and theproportion of diunsaturated isomers of the C37 methyl alkenone (theso-called “unsaturation index”) has been widely adopted by geochemistsas a proxy for past sea surface temperatures. Isochrysis, is one ofseveral species of haptophyte marine microalgae including the widelydistributed coccolithophore Emiliania huxleyi and the closely relatedspecies Gephyrocapsa oceanica that biosynthesize alkenones and therelated alkenoates and alkenes, known collectively as PULCA.

Alkenones are thought to reside in cytoplasmic lipid bodies and can bemore abundant than TAGs especially in the stationary growth phase. Undernitrogen or phosphorus limitation, up to 10-20% of cell carbon in thestationary phase is accumulated as predominantly triunsaturatedalkenones. Evolutionarily, alkenones may have been favored over TAGsbecause their trans-double bond geometry provides a more photostableform of energy storage. This unusual geometry has also been suggested tocontribute to their limited degradation by grazers in surface waters ofthe ocean.

Haptophytes had been included in several reviews and other reportsrelated to biofuels, but until recently alkenones were not discussed inany of these studies. In one study of 55 microalgal species forbiodiesel production, Isochrysis galbana proved to be average in bothbiomass yield and lipid productivity. Average lipid content in 15nutrient-replete and nitrogen-deficient cultures was 25% and 29% dryweight, respectively.

We were attracted to haptophytes in part because Isochrysis is one ofonly a select number of algal species formed industrially, harvested forpurposes of mariculture, and therefore is representative of the scalenecessary for biofuel production. In an effort to produce biodiesel(FAME) from Isochrysis, we recently described results from theacid-catalyzed esterification of the total hexanes extract (“biofueloil”). This material contained a significant amount of alkenones (14%w/w), and contamination by these high-melting (˜70° C.) components isdetrimental to cold flow fuel properties. More recently, a method forproducing an alkenone-free Isochrysis biodiesel was reported using asaponification/separation procedure. While this sequence adds additionalsteps to the overall process, in addition to supplying a superiorquality biodiesel, it also generates an alkenone-rich neutral lipidfraction as a potential secondary product stream.

We argue that alkenones represent a potentially fruitful and as yetunexplored renewable carbon source with structures particularly wellsuited for a number of catalytic processes. Specifically, alkenonesfeature long olefinic carbon-chains, favorable carbon-to-hydrogenratios, and few heteroatoms (i.e. no sulfur or nitrogen and C:O˜37-40:1, ref. FIG. 2). Key differences relative to fatty acids includea much longer hydrocarbon backbone, more widely spaced trans-doublebonds, and a ketone functional group (FIG. 14). Alkenones are alsofundamentally different than the terpenoid botryococcenes that havereceived significant attention as a potential algal biofuel source,despite the noted slow growth habit of B. braunii which poses concernsabout its suitability as a biofuel feedstock. PULCAs thus represent anunexplored source of renewable carbon biosynthesized by robust algalspecies that could provide access to a unique suite of productsunobtainable from other oil feedstocks.

Herein we report a method a series of selective extraction techniquesfor the parallel production of biodiesel and isolation of severalvaluable co-products including an alkenone hydrocarbon mixture of thekerosene/jet fuel range (primarily C10-, C12-, and C17-hydrocarbons) andfucoxanthin, a high-valued carotenoid, from marine microalgae.Isochrysis is produced industrially for purposes of mariculture and hasbeen included in several reviews and numerous reports related tobiofuels. Aside from its availability on large-scale, other attractiveattributes of Isochrysis as a biofuel feedstock include favorable growthcharacteristics and high lipid content. While there has been muchdiscussion about the potential for the isolation/production of valueadded co-products to augment algal biofuel production (the so-called“biorefinery” concept), to the best of our knowledge this is the firstreport with experimental data from a successful method for combinedbiodiesel production and valuable co-product isolation from an algaefeedstock.

Materials and Methods

1. Microalgal Species and Culture Conditions.

The marine microalgae Isochrysis sp. “T-iso” used in the present studyalthough Isochrysis sp. “C-iso” is also suitable. The marine microalgaeIsochrysis sp. “T-iso” was purchased from Reed Mariculture (strainCCMP1324) (Santa Cruz, Calif.) who has grown this species for nearly 20years as a primary feed in shellfish and shrimp hatcheries. The algaewere grown in greenhouse ponds under natural sunlight in a modified F/2media. Average water temperatures were 18 to 20 C. Approximately 1kilogram of wet biomass (20% biomass w/w) was harvested bycentrifugation and decanting of the supernatant and then lyophilized in˜30 g batches which gave ˜150 g of dry Isochrysis sp. biomass as agreenish, dark-brown solid.

2. Extraction of the Biofuel Oil from the Algal Biomass.

The dry Isochrysis culture was extracted in 30 to 50 gram batches withn-hexanes in a Soxhlet extraction apparatus. The Soxhlet apparatus wasallowed to cycle for 24-48 hours (until the color of the solvent was afaint yellow). Hexanes were removed with a rotary evaporator, and theweight of the n-hexanes-extractable material (now referred to as thebiofuel oil) was recorded. The residual biomass was retained from theextraction thimble for further use.

3. Isolation of Fatty Acids and Lipids from the Biofuel Oil.

After extraction from the biomass, the biofuel oil was processed in atransesterification reaction by treating the biofuel oil with KOH at 60°C. for 3 hours. The resulting saponified acylglycerols were selectivelypartitioned into water while the neutral lipids extracted withn-hexanes. Reacidification of the aqueous phase with HCl and extractionwith n-hexanes produced the free fatty acids (FFAs). The overall massrecovery for combined FFAs and neutral lipids from the algal oil istypically quantitative (40% neutral lipids +60% FFAs).

4. Isolation and Purification of Alkenones from the Neutral Lipids.

Neutral lipids (10 g) were dissolved in a minimal amount ofdichloromethane and flushed through silica gel (230-400 mesh, 100 g)with pressure using dichloromethane (approximately 150 mL) as eluent.The solvent was then removed on a rotary evaporator, and the resultingorange-colored solid was recrystallized in n-hexanes to give purealkenones (typically 4 g) as a white solid.

5. Alkenone Cross Metathesis and Analysis of Alkenone Derivatives.

The purified alkenones were further chemically modified by crossmetathesis reaction wherein 2-butene (i.e. butenolysis) was usedalthough other substitutions are possible as well. 2-Butene (0.2 mL, 15equiv.) was condensed in a reaction flask at −78° C. under a nitrogenatmosphere. Alkenones (100 mg), methyl stearate (methyl octadecanoate)(56 mg), dichloromethane or toluene (1.0 mL), and catalyst (2 mol %, 2-3mg) were then added and the resulting heterogeneous mixture was placedin a refrigerator (4° C.) or ice bath (0° C.) for the allotted time.Reactions conducted were quenched with ethyl vinyl ether (0.9 mL, 50equiv.) and stirred for 15 minutes before concentrating on a rotaryevaporator and analyzing by ¹H NMR and gas chromatography.

6. Analysis of Alkenones and Alkenone Derivatives.

Analysis by ¹H Nuclear Magnetic Resonance (1H NMR) Spectroscopy.

¹H NMR spectra of the purified alkenones and cross metathesis reactionmixtures were obtained under ambient conditions using CDCl3 as solvent,which also served as internal reference (shift value of residual protonat 7.26 ppm).

Analysis by One-Dimensional Gas Chromatography with Flame IonizationDetection (GC-FID) and Gas Chromatography-Mass Spectrometry (GC-MS).

The purified alkenones and butenolysis reactions were analyzed on aHewlett-Packard 5890 Series II GC-FID. Samples (1 μl) were injectedcool-on-column and separated on a 100% dimethyl polysiloxane capillarycolumn (Restek Rtx-IMS, 30 m length, 0.25 mm I.D., 0.25 μm filmthickness) with H₂ as the carrier gas at a constant flow of 5 mL min⁻¹.The GC oven was programmed from 70° C. (7 min hold) and ramped at 6° C.min⁻¹ to 320° C. (15 min hold). Percent conversions for the butenolysisreactions were determined by comparison of integration ratios forcombined alkenones (rt=44-48 min) to methyl stearate (retentiontime=27.5 min) relative to a starting alkenone/methyl stearate standardmixture. Select samples were also analyzed by GC-MS on an Agilent 6890GC with a 5973 MSD. Splitless 1 μL sample injections, were separated ona DB-XLB capillary column (60 m×0.25 mm×0.25 μm film thickness) usinghelium as the carrier gas (10.5 psi constant pressure), and thefollowing GC temperature program: 4 min at 40° C. and ramped to 320 at5° C./min (held 15 min).

Analysis by Comprehensive Two-Dimensional Gas Chromatography with FlameIonization Detection (GC×GC-FID) and Time of Flight Mass Spectrometer(GC×GC-TOF).

Select cross metathesis reaction mixtures were analyzed by GC×GC-FID andGC×GC-TOF MS according to previous described methodologies.

7. Ethanol Extraction of the Isochrysis Biomass.

After the Soxhlet extraction with n-hexanes, the residual biomass wassubmerged in ethanol (200 ml) for an allotted time. Care was taken atthis stage to ensure that the samples and subsequent materials wereexposed minimally to light. The biomass was then removed by filtrationinto a tared round bottom flask and the ethanol removed with a rotaryevaporator. Weights of the ethanol-extracted materials were recorded nowreferred to as the biomass oil.

8. Analysis and Isolation of Biomass Oil-Derived Co-Products.

Analysis by ¹H Nuclear Magnetic Resonance (¹H HMR) Spectroscopy.

¹H NMR spectra of the biomass oil, a fucoxanthin-enriched biomass oil,and a fucoxanthin standard were obtained on a Varian Inova 500 MHzspectrometer under ambient conditions using CDCl3 as solvent, which alsoserved as internal reference (shift value of residual proton at 7.26ppm). The fucoxanthin-enriched biomass oil was obtained by flashchromatography of biomass oil on silica using an automated Combiflash Rfsystem (Teledyne Isco): 1.9 g biomass oil, 24 g silica cartridge, 15minute run time, gradient from 100% hexanes to 100% ethyl acetate.Fractions that were bright red in color and mostly pure by TLC (1:1hexanes ethyl acetate, Rf fucoxanthin=0.36) were combined into a taredround bottom flask and concentrated on a rotary evaporator in the dark.The weight of the fucoxanthin-enriched biomass oil was recorded, and thefucoxanthin content analyzed by ¹H NMR and HPLC (vide infra).

Absorbance Spectroscopy.

Fractions obtained by chromatography of the neutral lipids on silicawere red in color, and their pigment content was examined by absorbancespectroscopy. These fractions were concentrated in vacuo and redissolvedin n-hexanes to a concentration of 50 mg/mL. A fucoxanthin standard waspurchased (Sigma-Aldrich), and a sample prepared as above forcomparison. Absorbance between 300 and 800 nm was measured using a JascoV-670 spectrophotometer.

Analysis and Quantification of Fucoxanthin by HPLC.

Fucoxanthin contents in the biomass oil were quantified using a VarianProStar HPLC system. The system consisted of a binary pump, 410auto-sampler, and Photodiode Array Detector. Separation was carried outwith a C18 column (Waters length 250 mm×i.d 4.6 mm×particle size 5 μm).The mobile phase (100% methanol) was eluted at a flow rate of 1 mL/min.Detection wavelength was set at 446 nm. Quantification of fucoxanthinwas carried out by means of a calibration curve, constructed byanalyzing fucoxanthin samples (purchased from Sigma-Aldrich) atconcentrations of 0.016-1.0 mg/mL with R2=0.9987.

Results and Discussion

Hexanes Extraction for Biodiesel Production.

Previously, we have reported on the production of a biodiesel fromIsochrysis using standard methods involving extraction of dry algalculture with n-hexanes. After removal of the n-hexanes in vacuo, theresulting green/black grease-like biofuel oil can be converted to acrude biodiesel by acid-catalyzed esterification. Biodiesel produced bythis method is approximately 40% non-fatty acid methyl ester (non-FAME,i.e. non-biodiesel) components that include a unique class of lipidsbiosynthesized by Isochrysis known as polyunsaturated long-chainalkenones. The significant amount (14% w/w) of these high-meltingalkenones leads to severe cold-flow fuel property issues.

An alkenone-free Isochrysis biodiesel can be achieved by treatment ofthe biofuel oil with potassium hydroxide resulting in saponification ofthe triglycerides and formation of the corresponding water-solublecarboxylate salts (soaps). Alkenones along with other neutral lipids arethen selectively partitioned into a hexanes layer before the aqueoussoaps are re-acidified and converted to biodiesel. This purifiedbiodiesel has markedly improved cold-flow with no trace of alkenonecontamination and is now 95% FAME. The mass balance for thesaponification process is quantitative (60% FFAs+40% neutral lipids) anddoes not affect the FAME profile of the resulting biodiesel.

While saponification introduces additional steps into the biodieselsynthesis, not only is the biodiesel obtained of higher quality, it alsoallows for the recovery of a neutral lipid fraction from the originalbiofuel oil as a potential secondary product stream in line withrecommendations from the U.S DOE “National Algal Biofuels TechnologyRoadmap”. Our primary interest in this regard has been with thealkenones which comprise approximately 40% (w/w) of the neutral lipidsobtained by saponification and separation of the biofuel oil.

Isolation and Purification of Alkenones as a Byproduct of BiodieselProduction.

Prior to attempting any reactions, we isolated and purified thealkenones from the neutral lipid fraction containing other compoundsincluding pigments such as chlorophylls and carotenes. This waschallenging due to the low solubility of alkenones in a variety oforganic solvents (e.g. n-hexanes, diethyl ether, acetone, ethylacetate). After some optimization, the dark-colored pigment-containingmaterial could be removed by flushing the material through silica usinga minimal amount of dichloromethane (DCM) as eluent. Upon removal of thesolvent, the resulting orange-colored solid was further purified byrecrystallization with n-hexanes affording analytically pure alkenonesas a white solid (FIG. 3). This procedure generally resulted in 40%isolated yield (w/w) from the neutral lipids or 3.2% of the Isochrysisdry culture, which is close to the total alkenone content of 5% that wedetermined previously. Analysis of the purified alkenones by gaschromatography and comparison to standards revealed the presence ofC37:3, C37:2, C38:2, and C38:3 alkenones along with small amounts of theC39:3 and C39:2 with the most abundant being the methyl 37:3 (where C#:#refers to the number of carbon atoms:number of double bonds, see FIG.2).

Cross Metathesis of Alkenones with 2-Butene.

Results from the cross metathesis reactions of isolated alkenones with2-butene using Grubbs' first- (Ru-I) and second-generation (Ru-II)catalysts, and Ru-HG are summarized in FIG. 15.

Olefin metathesis has long been embraced by the synthetic organic andpolymer communities, often used to create larger molecules from smallalkene-containing starting materials as in the case of cross metathesis(FIG. 11). These reactions typically occur with the extrusion ofethylene gas, which serves as an entropic driving force. The oppositeprocess, i.e. addition of ethylene across a double bond (“ethenolysis”),would thus create two smaller subunits. Ethenolysis of FAMEs and otherfatty acid derivatives using Grubbs'-type ruthenium initiators has beenabundantly reported as a method for producing valuable smallerhydrocarbon mixtures from renewable feedstocks.

One challenge associated with ruthenium-catalyzed ethenolysis is thatthe reaction requires propagation of a ruthenium methylidene speciesthat is prone to decomposition (X═H, FIG. 12). Additionally, theterminal olefin products can undergo the reverse self-metathesis and soyields tend to be modest (˜40-60%). One strategy to improve thisapproach is to use 2-butene in place of ethylene (X=Me), thus avoidingformation of a ruthenium methylidene and producing methyl-capped alkeneproducts that are less reactive toward self-metathesis.

Patel and coworkers reported the rapid and high-yielding crossmetathesis reaction of methyl oleate (Methyl (9Z)-octadecenoate) with2-butene using the second-generation Hoveyda-Grubbs catalyst (Ru-HG) toproduce methyl 9-undecenoate and 2-undecene (FIG. 13). Applied tolong-chain alkenones, certain fundamental differences between thealkenones and FAMEs made success of this reaction uncertain (ref. FIG. 2and FIG. 14). First, again the alkenones contain trans-alkenes asopposed to the more metathesis-reactive cis-configured double bondsfound in FAMEs. Second, alkenones have limited solubility in the organicsolvents used to perform olefin metathesis, particularly at the coldtemperatures required to condense 2-butene (trans-2-butene bp=0° C.). Itwas therefore unclear whether the alkenones would even dissolve and ifso whether the catalyst would engage the alkenone trans-double bonds atthese low temperatures.

All butenolysis reactions were performed using an excess of 2-butene (15equiv., calculated as 5 equiv. per alkene for the most abundant (37:3)alkenone in the starting mixture) to drive the equilibrium towardproducts and 2 mol % (calculated as above) of the catalyst. After 18 hat 4° C., the alkenones were consumed when using catalysts Ru-II andRu-HG (entries 1-3), whereas Ru-I gave only 70% conversion under thesesame conditions (entry 4). Patel and coworkers reported very lowconversions (<1%) for the butenolysis of methyl oleate with cis-2-butene(10 equivalents) using both Ru-I and Ru-II, however those reactions wereconducted at lower temperature (−5° C.), catalyst loading (0.1 ppt), andtimes (2 h). Near quantitative conversion of methyl oleate was reportedby Patel et. al when using Ru-HG at −5° C. for two hours and upon closerexamination was essentially complete within 30 minutes. Butenolysis ofalkenones using either cis- or trans-2-butene with Ru-HG appearedsimilarly rapid with 100% conversion observed after 1 h (Entries 6 and7, FIG. 15).

Proton NMR was not very effective for monitoring the alkenonebutenolysis reactions as the spectra for the starting alkenones andbutenolysis product mixture were essentially identical. By GC-FID,however, it was clear that no alkenones remained for those reactionswith 100% conversion (FIG. 4). What was perhaps equally diagnostic wasthe dramatic change in reaction appearance upon successful butenolysis.At the start of the reaction the alkenones appear completely insoluble.After conversion to butenolysis products using Ru-II or Ru-HG themixture becomes homogenous as an indication of high conversion.

To better understand the kinetics of the alkenone butenolysis, weattempted to monitor the progress of the reaction using the standardmethod employed by Patel and coworkers for their butenolysis of methyloleate. Namely, aliquots were removed from the reaction mixture viasyringe that were then quenched by the addition of ethyl vinyl ether andanalyzed by GC-FID. Results from this experiment are presented in FIG. 5where percent conversion was calculated by comparing the GC-FID arearatio of alkenones to methyl stearate as an inert internal standard pre-and post-butenolysis. The kinetics of the reaction were unexpected,showing an apparent decrease in alkenone conversion during the first 10minutes. We interpret these results to represent a dynamic system ofalkenone solvation and butenolysis. Initially, alkenone concentration inthe solvent sampled is low due to poor solubility. Over time, dissolvedalkenone concentration increases resulting in a lower calculated percentconversion. After 10 minutes the rate of butenolysis appears to exceedthe rate of alkenone solvation and the calculated percent conversionincreases.

To obtain accurate rate data, it was therefore necessary to performmultiple separate butenolysis reactions quenched at different timeincrements. Entries 8-17 in FIG. 15 therefore represent results fromindividual reactions followed by analysis of the entire reactionmixtures. Several interesting observations were made during the courseof this somewhat laborious process. As expected, catalyst Ru-HGoutperformed catalyst Ru-I, with only 16.7% conversion recorded for Ru-Iafter six hours (Entry 12). The reaction with Ru-HG was exceptionallyfast, giving greater than 90% conversion after only 20 minutes andessentially complete conversion within 30 minutes (Entries 9 and 10).These values are very similar to those reported by Patel and coworkersfor the butenolysis of methyl oleate despite the structural differencesnoted earlier between the alkenones and this FAME. The reaction withtrans-2-butene gave significantly lower conversion at the 15-minute mark(Entry 16), perhaps the result of a more rapid initiation ofcis-2-butene by the parent catalyst, but after 30 minutes stillgave >95% conversion (Entry 17). DCM was chosen as a solvent for thesereactions as it had demonstrated the greatest alkenone solubility,although its use is undesirable for any “green” process. We thereforeexamined the reaction in toluene (PhMe), a more tolerated solvent thatshowed some alkenone solubility and is often used in olefin metathesisreactions. Reactions performed in toluene gave lower conversions at both10 and 20 minutes when compared to those in DCM (Entries 8 and 9 vs 13and 14), likely a reflection of diminished alkenone solubility.Nonetheless, the butenolysis in toluene was still very efficient givingcomparable conversion (98%) after 30 minutes at 0° C. (Entry 15).

FIG. 13 shows the expected products from complete butenolysis of themajor alkenone (methyl 37:3) constituent isolated from Isochrysis. Thetrue product mixture from our butenolysis reactions is of course muchmore complex because we started not just with pure C37:3 methylalkenone, but the complete set of alkenones extracted from the biomassthat ranged from 37-39 carbons with 2-3 double bonds and methyl or ethylketones. Add to this the potential for incomplete butenolysis productsalong with cis- and trans-isomers and the mixture becomes quite complex.For this reason, GC×GC was used to analyze select butenolysis reactions.GC×GC has been increasingly applied in hydrocarbon analysis, petroleumresearch, and oil spill science as it has many advantages overone-dimensional GC: its higher chromatographic resolution increases thesignal to noise ratio and compounds are separated based on two physicalproperties (e.g. vapor pressure and polarity depending on choice ofcolumn stationary phase), leading to a grouping of chemical classes in aGC×GC chromatogram. Coupling of GC×GC with a flame ionization detector(FID) allows for the quantification of numerous unidentified compoundsbecause most hydrocarbons have similar response factors. Coupled to atime of flight mass spectrometer (TOF-MS), the enhanced resolution andincreased signal to noise afforded by GC×GC allows for more accuratespectral identification of many compounds.

Specific alkenones in our samples were identified by their massspectrum, comparison to published elution order on gas chromatographiccolumns, textbook descriptions of alkenones, and other more recentstudies detailing alkenone structure analysis. Relative amounts ofindividual alkenones were determined by GC-FID and these valuescorrelated well with those previously reported for the same Isochrysisstrain used in our study (FIG. 16). Based upon this alkenone profile, wecan then predict the products from our butenolysis reaction. Forinstance, each of the 37 and 38 alkenones should produce 2-heptadecene(2) and two equivalents of 2,9-undecadiene (3) (ref. FIG. 13).Butenolysis of the 37 and 39 alkenones would similarly give 3 along with8-decen-2-one (1). Considering the relative alkenone percentages, thiswould then give the distribution outlined in FIG. 16 with 1, 2, and 3accounting for 83% of the products.

FIG. 6 is a typical GC×GC-FID chromatogram of the butenolysis productsobtained by reaction of our alkenone mixture with cis-2-butene usingcatalyst Ru-HG. For reaction times down to 30 minutes in DCM at 0° C.,the butenolysis was complete (ref Entry 3, FIG. 15). Each of theexpected major products 1, 2, and 3 can be clearly identified.Additionally, for both 1 and 3, two peaks are clearly visible withintegration ratios from the GC×GC-FID of 3.9:1 that we have assigned asthe trans- and cis-isomers respectively. This is based in part on theearlier work from Patel and coworkers who also reported a 4:1 trans:cisratio for 2-undecene obtained by butenolysis of methyl oleate. Threepeaks in our alkenone butenolysis product mixture were identified withm/z=152 in a ratio of 17.9:7.5:1 that have been assigned to the threepossible isomers for 2 (E,E-, E,Z- and Z,Z-). Additional signals includecis- and trans-9-undecen-3-one (m/z=168) obtained from the 38:3 ethylalkenone contained in our sample (ref. FIG. 2) and catalyst-derived1-isopropoxy-2-(propenyl)benzene (m/z=176).

Altogether the ratio of butenolysis products 1:2:3 by GC×GC-FID analysiswas typically 1:2.0:2.5 respectively, which is slightly different thanwhat was predicted in FIG. 16 (1:2.3:3.4). Closer inspection of theGC×GC-TOF chromatogram data revealed several unexpected productscompared to those presented in FIG. 16 that might help explain thisdiscrepancy (FIG. 7). As is typical of GC×GC data, certain regions ofthe chromatogram contain different sub-classes of compounds. Forinstance using drilling mud samples containing a series of linearalkenes (“n-alkenes”) as a standard reference, an “n-alkene” regioncould be identified containing not only the expected C17 and C19, butalso trace C16 and C18 olefins. For each, two peaks were observed withpeak area ratios of approximately 1:4, consistent with our previous cis-and trans-isomer assignments. 2-Octadecene could have arisen from oursample containing very small amounts of a 38-methyl and/or 39-ethylalkenone. By a similar argument, hexadecene formation could have beenformed from a methyl C36 alkenone that we did not detect in our samplenor has a C36 alkenone been reported for Isochrysis elsewhere.Alternatively, some double bond isomerization occurred during the courseof the cross metathesis which has been reported for metathesis reactionsof other aliphatic systems. It is interesting, however, that onlyC16-C19 alkenes were detected for our butenolysis conducted at bothshort (e.g. 30 min) and longer (18 h) reaction times rather than thelarger range of alkenes that could be envisioned from an isomerizationprocess. Another possibility is that Isochrysis biosynthesizes traceamounts of alkenones with differing double bond positions. This wouldalso perhaps explain the peak with m/z=168 in the diene region of thechromatogram that we have tentatively identified as 2,10-dodecadiene.Efforts are ongoing to characterize completely and better understand themixture of products generated in this and other related reactions as itrelates to both product use and alkenone structure elucidation.

During the course of isolating and purifying alkenones from this neutrallipid fraction by chromatography on silica, we obtained a few smallfractions that appeared as bright red solutions. Recently there havebeen a few reports describing the isolation and quantification of thecarotenoid fucoxanthin from Isochrysis. Fucoxanthin is a structurallycomplex oxidized form of β-carotene (a xanthophyll, FIG. 8) that hasreceived significant interest for its range biological activitiesincluding anti-inflammatory, anti-angiogenic, anti-diabetic,anti-obesity, and anti-carcinogenic effects. Indeed, a UV-Vis spectrumof our red fractions showed characteristic peaks at 428, 446 and 475that were consistent with the spectrum obtained for the fucoxanthinstandard and reported elsewhere (FIG. 8).

Interestingly, hexanes had been shown to be a poor solvent forfucoxanthin extraction from algal culture, with alcoholic solvents likeethanol and methanol proving far superior. For instance in the study byKim et al., extraction with hexanes produced 1.04 mg of fucoxanthin from1 g of dry Isochrysis culture powder (1.04 mg/g DW) whereas ethanol gave19.76 mg/g DW under identical conditions. These results suggested thatafter our hexanes extraction that we ultimately use to make biodiesel,the majority of fucoxanthin remains in what was previously waste biomassand might still be recoverable

Sequential Hexanes/Ethanol Extraction for the Co-Production of Biodieseland Fucoxanthin.

Hexanes extraction of 30 g of dry Isochrysis culture was performed ashad been previously described and produced 5.85 g biofuel oil,consistent with our prior reports (FIG. 17). The post hexanes-extractedbiomass was then removed from the cellulose extraction thimble andsubmerged in ethanol. Due to the known photolability of fucoxanthin andother carotenes, the ethanol extraction along with all subsequent stepswas performed in the dark to minimize exposure to light. The yield ofbiomass oil after 24 h at room temperature was 7.3% (w/w) andfucoxanthin content was 19% (w/w) compared to only 3% (max.) fucoxanthincontent for the biomass oil (FIG. 9). For further confirmation, afucoxanthin-enriched biomass oil could be obtained by unoptimizedchromatography on silica to produce a product (0.54 g from 1.89 gbiomass oil) that was now 44% fucoxanthin according to HPLC analysis.The ¹H NMR spectra for both the biomass oil and this enriched biomassoil showed peaks consistent with that for the fucoxanthin standard (FIG.10).

Kim and coworkers reported a significant correlation between theduration of ethanol extraction and the amount of fucoxanthin obtained.Specifically, maximum yields were obtained after only 5 minutes at roomtemperature (20.28 mg/g DW after 5 minutes vs. 17.38 mg/g after 24 h).The authors attribute this difference as being due to the sensitivity offucoxanthin toward decomposition. To test the impact of time on our ownfucoxanthin ethanol extraction, dry Isochrysis culture (50.6 g) wasagain first extracted with n-hexanes in a Soxhlet apparatus. Thepost-extracted biomass was then split (2×22.5 g), with one halfextracted in ethanol for 1 h and the other extracted for 24 h at roomtemperature. Somewhat surprisingly, the yield of fucoxanthin wassubstantially higher for the 24 h extraction. This was not a function ofone biomass oil being more enriched in fucoxanthin (21.5% and 20.0% forthe 24 h and 1 h extractions respectively), but rather the amount ofalgal oil that was obtained from the different extraction techniques(2.22 g vs. 0.97 g). Kim et al. described the use of dried biomass“powder” for their fucoxanthin extraction study. Additionally, thoseexperiments were conducted on a significantly smaller scale (100 mg vs.20-30 g dry biomass) which might also contribute to the discrepancybetween our extraction time data and theirs. Assuming that the samplehad not been split and the entire 45 g of post hexanes-extracted biomasswas extracted with ethanol for 24 h to produce 4.44 g (2×2.22 g) biomassoil, this would correspond to 18.8 mg/g DW. Combined with thefucoxanthin contained in the biofuel oil and data obtained from the 30 gbiomass extraction, average total fucoxanthin extracted from ourIsochrysis samples is 21.73 mg/g DW. This value is in the range of themaximum value reported by Kim et al. by extraction with ethyl acetatefor 1 h at room temperature (20.98 mg/g DW) as well as the total (sum ofE,Z-isomers) fucoxanthin content in Isochrysis biomass reported by Crupiand coworkers (19.82±3.72).

On average, 75% of the total extracted fucoxanthin is contained in ourbiomass oil, which is similar to that obtained by Kim et al. using acomplimentary two-phase lipid/fucoxanthin separation procedure. Unlikethe two-phase separation procedure, however, our method does not disruptor alter the biomass-to-biodiesel process. Rather it is the biodieselwaste-stream to which value is being added, not unlike other reportsdescribing the use of residual algal biomass as feed or its gasificationto fuel. Yields of Isochrysis are estimated to be 175 metric tons ofbiomass dry weight hectare⁻¹ year⁻¹ (outdoor pond). At approximately 2%(w/w) fucoxanthin content, this would correspond to 3.5 metric tons offucoxanthin hectare⁻¹ year⁻¹. The current market for fucoxanthin is as adietary supplement using mixtures isolated from several edible brownseaweeds. Given the range of reported biological activities, withincreased supply there could also be an increase in its applicationsresulting in a potentially not-insignificant offsetting of the fuelcost.

There is great interest in the co-production of value added chemicals asa means for improving the economic viability of algal biofuels. Byexploiting differences in solvent extraction efficiencies, a tandembiomass extraction protocol has been developed that allows forsimultaneous biodiesel production and isolation of a high-valuecarotenoid fucoxanthin from the marine microalgae Isochrysis.Specifically, extraction of dry Isochrysis biomass with hexanes using aSoxhlet apparatus provides acylglycerols that can then be converted tobiodiesel by means of a transesterification reaction. That same residualbiomass can then be extracted with ethanol to provide an algal oilenriched in fucoxanthin (20% w/w). Quantification of the amount offucoxanthin in the ethanol algal oil revealed that this sequentialextraction is quite selective and with total values near the maximumfound in other reports describing fucoxanthin from Isochrysis. Effortsare ongoing to optimize and analyze this procedure as a general strategyfor the co-production of fuel and value-added compounds from Isochrysisand other promising algae feed-stocks.

Example 3

This example demonstrates the co-purification, from a single batch ofalgae, of an alkenone-enriched sample in conjunction with an othercommercially valuable second molecule (e.g. therapeutic molecule,neutraceutical, fuel, food-stuff, raw material, etc.).

The co-production of alkenones and alkenone derivatives from what inmany instances is the waste-stream of a second commercially valuableproduct may significantly increase the commercial attractiveness ofalkenone extraction because the cost of culture, growth, and preparationmay be considered as being born by the production of the second product.Furthermore, in the production of biodiesel (e.g. FAMEs) and biofuels, asignificant portion of algal biomass (often containing alkenones), isdiscarded as the waste-stream.

In this example, both FAMEs and a commercially valuable second molecule(e.g. fucoxanthin, astaxanthin, beta-carotene, and other carotenoids)are produced, and an alkenone-enriched fraction is obtained as well.

1. Microalgal Species and Sample Preparation.

The marine microalgae Isochrysis sp. “T-iso” is used in the presentexample although Isochrysis sp. “C-iso” is also suitable as well as anyother suitable such algae species described herein. The algae are grownin greenhouse ponds under natural sunlight in a modified F/2 media.Average water temperatures are 18° C. to 20° C. A sample of algal wetbiomass is harvested and then lyophilized to yield dry Isochrysis algalculture 1. In some embodiments, the algal culture 1 is not dried priorto solvent extraction.

2. Extraction of the Algal Culture.

The Isochrysis algal culture is mixed with one or more liquids toproduce a two-phase system. In the first instance (e.g. dry Isochrysisand a polar solvent such as n-hexanes), the two-phase system comprises asolid and a liquid. In the second instance, a liquid two-phase system isproduced comprising a first polar phase and a second less polar phase.In either instance, after they are produced, the two phases areseparated by the appropriate methods as is known to the art, yielding analkenone-enriched phase (i.e. a sample comprising alkenones, lipids,fatty acids, etc., biofuel oil) and a second phase enriched with theother commercially valuable product or molecule.

In some embodiments of this example, one or more liquids are added tothe algae from a group comprising alkanes, alkenes, alkynes, alcohols,ketones, amines, amides, esters, ethers, acids, organic compounds,carboxylates, halogenated hydrocarbons, surfactants, detergents, polarsolvents, water, ethanol, methanol, butanol, alcohols, n-hexanes,chloroform, dichloromethane, chloromethane, dichloroethane,tetrahydrofuran, methyltetrahydrofuran, acetonitrile, nitromethane,propylene carbonate, acetone, and liquid hydrocarbons. In a specificembodiment of the example, water, a polar solvent (e.g. ethanol,methanol), and n-hexanes are added to extract the dry culture. Inanother embodiment, water, an alcohol (e.g. ethanol, methanol, butanol),and chloroform are added. In yet another embodiment, water, a polarsolvent, and a liquid hydrocarbon are added to the extraction. In onecase where a wet (i.e. aqueous) algal culture is used, a polar solventand n-hexanes are used. In another case where a wet algal culture isextracted, a polar solvent and chloroform are added.

Once the two phases are separated, the alkenone-enriched phase (e.g.biofuel oil in the case of dry algae extracted with a non-polar solventor the lower polarity phase in the case of algae extracted with ethanol,water, and n-hexanes) is further purified.

In one embodiment, a Soxhlet extraction apparatus or similar device isutilized for the extraction. Additionally in some embodiments, care maybe taken at this stage to ensure that the samples and subsequentmaterials are exposed to a minimal amount of light.

3. Isolation of Fatty Acids and Lipids from the Alkenone-EnrichedSample.

After the algae extraction and phase separation, the alkenone-enrichedsample (e.g. sample comprising the biofuel oil) is processed in anesterfication reaction to produce fatty acid methyl esters (i.e. FAMEs)from fatty acids present in the sample. The FAMEs are then separatedfrom the sample (e.g. In one embodiment, this is accomplished bytreating the sample with KOH at 60° C. for 3 hours; the resultingsaponified acylglycerols are selectively partitioned into water whilethe neutral lipids are extracted with n-hexanes. Reacidification of theaqueous phase with HCl and extraction with n-hexanes may produce thefree fatty acids (FFAs).) Alkenones are further derivatized and/orpurified and/or analyzed as described in Example 2 and elsewhere herein.

All publications patents and published patent applications referred toin this application are specifically incorporated by reference in theirentirety as if each individual publication, patent or published patentapplication was specifically and individually indicated to beincorporated by reference. In case of conflict, the present application,including its specific definitions herein, will control. Incorporatedreferences include Lindell et al. Publication No. US2014-0171608A1 andBidle et al. U.S. Pat. No. 8,557,514.

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, many equivalents to the specificembodiments of the invention described herein. Such equivalents areintended to be encompassed by the following claims.

The invention claimed is:
 1. A method of isolating from algae, an algalbiomass and a biofuel oil, each comprising at least one product,comprising the steps of (a) growing an algal mariculture capable ofproducing alkenones and a co-product; (b) extracting the algal culturewith a non-polar liquid hydrocarbon solvent comprising one or morealkanes having from 1 to 22 carbons to produce an extraction mixture;(c) separating the extraction mixture into an algal biomass fraction anda biofuel oil fraction which comprises alkenones; and (d) isolating thealkenones from the biofuel oil fraction and a co-product from the algalbiomass-fraction.
 2. The method of claim 1, wherein substantially purealkenones are isolated in step (d) by combining the biofuel oil fractionwith a polar or partially polar solvent selected from one or more ofchloromethane, dichloromethane, dichloroethane, tetrahydrofuran,dimethylformamide, acetonitrile, nitromethane, propylene carbonate,formic acid, butanol, isopropanol, methyltetrahydrofuran,trifluoromethylbenzene, ethyl acetate, ethyl ether, acetone, dimethylsulfoxide, alcohols, acetic acid, esters, ethers.
 3. The method of claim2, wherein the alkenones are recrystallized in a solvent selected fromone or more of dichloromethane, dichloroethane, chloromethane, toluene,tetrahydrofuran, dimethylether, diethyl ether, methyl-tert-butyl ether,n-hexanes methyltetrahydrofuran, or acetonitrile.
 4. The method of claim1, wherein the algal culture comprises an algal family selected from oneor more of the Isochrysis family, the Emiliania family, and theGephyrocapsa family.
 5. The method of claim 4, wherein the algal culturecomprises an algal species selected from one or more of Isochrysisgalbana, Isochrysis species T-Iso, Isochrysis species C-Iso, Isochrysislitoralis, Isochrysis maritime, Emiliania huxleyi, or Gephyrocapsaoceanica.
 6. The method of claim 1, further comprising harvesting anddrying the algal mariculture of step (a) by lyophilization, evaporationwith or without the addition of solvents, vacuum drying, drum drying,hot air exposure, dielectric drying, supercritical drying, natural airdrying, or a combination thereof.
 7. The method of claim 1, wherein thenon-polar liquid hydrocarbon solvent contains no fatty acids or fattyacid derivatives, and wherein the extraction mixture of step (b) issubjected to evaporation prior to step (c).
 8. The method of claim 1,wherein the isolated alkenones are chemically modified by a crossmetathesis reaction to produce alkenone derivatives.
 9. The method ofclaim 8, wherein the alkenones are chemically modified by an alkenolysisreaction to produce alkenone derivatives.
 10. The method of claim 8,wherein the alkenones are chemically modified by a butenolysis reactionto produce alkenone derivatives.
 11. The method of claim 8, wherein theisolated alkenone derivatives comprise from 5 to 20 carbon atoms. 12.The method of claim 1, wherein the non-polar liquid hydrocarbon solventcomprising one or more alkanes having from 1 to 22 carbons is selectedfrom benzene, toluene, cyclohexane, chloroform, ether, 1,4-dioxane,n-hexane, pentane, cyclopentane, iso-hexane, n-heptane, iso-heptane,octane, iso-octane, a neutral surfactant, a nonionic surfactant, or acombination thereof.